Shortwave Infrared technology - short wave infrared

 2024-10-02 12:33:55

Green Laser Pointernear me

With drop-in filters, rectangular filters and Rota-Pols for cine matte boxes, circular polarizing filters are labeled with “this side out”.

In still photography, SLR cameras and DSLR cameras have a mirror, which a linear polarizer can cross polarize, causing the image to darken or go black.

Lindsey Optics offers both circular and linear polarizers in professional cine sizes in 4.5" Round Drop-In, 138mm Round Drop-In, and 4"x5.65" and Rota-Pols in 4x5.65" and 6.6x6.6" all with anti-reflection coating.

NaCl is made up of two elements sodium and chlorine in the simple ratio of 1:1. The sodium atom donates one electron to the chlorine atom forming an ...

Having said that, these things are damn bright. If you hit a car driver at night with this, he'd be effectively blinded for at least a few seconds afterwards -- long enough to crash and die and have you go to prison for manslaughter. These are not toys for children. They should never be shined at people ever, and most especially not cars or planes. Finally, why green? Our eyes are most sensitive to green light. The same measured power output of a red laser would not produce a visible beam, because our eyes aren't as sensitive to red. By the time we could see a red laser, it would probably be reaching a dangerous level of intensity. BTG-6-plus Z-bolt offers several green laster pointers in the IIIa class. Note that these are often referred to as 5mW lasers, but they always have to be less. From everything I've read, there is a lot of variation in how much under 5mW the lasers are. I'm not sure how much to believe, but some claim that you can end up with as little as 1.5 mW from some of these products. For this reason, I chose the BTG-6-plus, because this particular product is guaranteed to be tested by Beam-of-Light to be between 4.5 and 5mW limit. Mine actually came with a hand-written sticker on it that said 4.92 mW. It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Green Laser pointer10000mw

It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Edmund Scientific Co | 1983 Holiday Sale Catalog 8310 Technology Telescopes. eBay.com. Edmund Scientific Co | 1986 Annual Catalog 8609 Technology Telescopes.

Polarizers used in cinematography are often inserted in a matte box so there's an opportunity to insert a circular pol backwards and it doesn't polarize when inserted incorrect.

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The short answer is that both Linear and Circular Polarizers do the same thing. The actual polarization effects such as reducing reflections on glass surfaces, increasing color saturation in foliage, darkening a blue sky are the same with both Linear and Circular polarizers.

Insert the included battery into the camera for charging. You can use the compact power adapter, or a computer to charge the battery. The procedure for using a ...

The M-238 is a high-force micropositioning linear actuator. It provides linear motion up to 50mm, a load capacity to 400 N and high velocity to 30mm/second. Its ...

Exterior flat lasers are used for checking/setting elevations, basic slope work and excavation. Fully automatic self-levelling capabilities, ...

The main problem that the circular polarizer addresses is cross polarization on other reflective surfaces in your system such as mirrors and beam splitters. Reflective surfaces polarize light . . . which is why a polarizer can reduce or eliminate those reflections. If you have a mirror or other reflective surface inside your camera, a linear polarizer can cross polarize the reflected image and possibly black out the image.

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I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Oct 22, 2024 — Causes of Fiber Cut and the Recommendation to Solve the Problem · 1) Arial or Overhead Installation. This form of installation required that ...

Finally, why green? Our eyes are most sensitive to green light. The same measured power output of a red laser would not produce a visible beam, because our eyes aren't as sensitive to red. By the time we could see a red laser, it would probably be reaching a dangerous level of intensity. BTG-6-plus Z-bolt offers several green laster pointers in the IIIa class. Note that these are often referred to as 5mW lasers, but they always have to be less. From everything I've read, there is a lot of variation in how much under 5mW the lasers are. I'm not sure how much to believe, but some claim that you can end up with as little as 1.5 mW from some of these products. For this reason, I chose the BTG-6-plus, because this particular product is guaranteed to be tested by Beam-of-Light to be between 4.5 and 5mW limit. Mine actually came with a hand-written sticker on it that said 4.92 mW. It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Circular polarizers for cinematography are marked to show proper orientation, but mistakes happen. If you have no mirrors or reflective surfaces in your system, such as a mirror or a beam splitter . . . then the Linear-Pol will not cause you any trouble and you can’t put it in the matte box backwards, which might save you some time and trouble.

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I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

With a circular pol, the quarter wave plate on the rear of the polarizer spins the light before it enters the camera lens so that it doesn't get cross polarized on any reflective surfaces in the system, such as the partial mirror in a video tap or a DSLR mirror.

The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

High PowerGreen Laser Pointer

The linear polarizer element in a circular polarizer needs to be out front, pointed at the world, with the quarter wave plate on the rear side, the camera lens side. A circular polarizer doesn’t work if you get it in backwards. With a screw-in filter that’s no issue, there's only one way you can screw it on the lens..

Collimated Beams · How to Collimate a Beam. A divergent beam can be collimated with a beam collimator device, which in simple case is essentially a lens or a ...

So how safe are these things (the sub-5mW class IIIa version)? They won't burn you. They won't cause permanent eye damage. Tests were performed on individuals who were scheduled to have an eye removed for medical reasons. For the purposes of the test, the eye was normally functioning. Test subjects stared directly at 5 mW lasers with there to-be-removed eye for five to fifteen minutes from various angles. No permanent eye damage occured. Some changes in tissue were noticed. Of course, in a real-world incident, laser light entering the eye would likely last for less than one second, as people naturally look away from bright things and close their eyes, so there is no real danger of direct damage. Having said that, these things are damn bright. If you hit a car driver at night with this, he'd be effectively blinded for at least a few seconds afterwards -- long enough to crash and die and have you go to prison for manslaughter. These are not toys for children. They should never be shined at people ever, and most especially not cars or planes. Finally, why green? Our eyes are most sensitive to green light. The same measured power output of a red laser would not produce a visible beam, because our eyes aren't as sensitive to red. By the time we could see a red laser, it would probably be reaching a dangerous level of intensity. BTG-6-plus Z-bolt offers several green laster pointers in the IIIa class. Note that these are often referred to as 5mW lasers, but they always have to be less. From everything I've read, there is a lot of variation in how much under 5mW the lasers are. I'm not sure how much to believe, but some claim that you can end up with as little as 1.5 mW from some of these products. For this reason, I chose the BTG-6-plus, because this particular product is guaranteed to be tested by Beam-of-Light to be between 4.5 and 5mW limit. Mine actually came with a hand-written sticker on it that said 4.92 mW. It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Our Rota-Pol a circular polarizer made to fit in 4"x5.65" cine matte boxes and allow quick and easy rotation by hand or with a motor:

So if you are asking the question: "Do I need a circular or linear polarizer?", we hope we've given you enough information to make that decision.

Pointer laser greenamazon

So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

Green laser background There is a class of lasers, IIIa, which by law must be less than 5mW (of measured optical output, not electrical input). This class is legal to sell in the United States, and legal to operate outside in the United States (local or state exceptions may exist) provided you don't do anything stupid. Shining the laser at aircraft in flight, or moving cars, or other equally moronic acts can easily land you in prison for an extended time (and rightly so). Apparently a man who wanted to see if he could hit airplanes as they were landing was in fact successful. Thankfully, none of the pilots crashed, but the man was reported to have received a seven year prison sentence. The next higher class, IIIb ranges from 5 to 500 mW. You can also legally purchase this class of laser in the United States. But there are restrictions on it's use, because these lasers are capable of permanently damaging vision. You can't use it in an environment where the beam could escape to the outside. To be explicit here, this means you can't legally use them outside. Now you may want to adopt a "no blood, no foul" attitude, and that's fine for you. But just know that if you ever make a mistake, or run into a narrow-minded individual, you don't have a legal leg to stand on - prepare for a good screwing. Furthermore, based on my own <5mW product, there is no reason outside of inferiority complex to get a higher power product for astronomical use. So how safe are these things (the sub-5mW class IIIa version)? They won't burn you. They won't cause permanent eye damage. Tests were performed on individuals who were scheduled to have an eye removed for medical reasons. For the purposes of the test, the eye was normally functioning. Test subjects stared directly at 5 mW lasers with there to-be-removed eye for five to fifteen minutes from various angles. No permanent eye damage occured. Some changes in tissue were noticed. Of course, in a real-world incident, laser light entering the eye would likely last for less than one second, as people naturally look away from bright things and close their eyes, so there is no real danger of direct damage. Having said that, these things are damn bright. If you hit a car driver at night with this, he'd be effectively blinded for at least a few seconds afterwards -- long enough to crash and die and have you go to prison for manslaughter. These are not toys for children. They should never be shined at people ever, and most especially not cars or planes. Finally, why green? Our eyes are most sensitive to green light. The same measured power output of a red laser would not produce a visible beam, because our eyes aren't as sensitive to red. By the time we could see a red laser, it would probably be reaching a dangerous level of intensity. BTG-6-plus Z-bolt offers several green laster pointers in the IIIa class. Note that these are often referred to as 5mW lasers, but they always have to be less. From everything I've read, there is a lot of variation in how much under 5mW the lasers are. I'm not sure how much to believe, but some claim that you can end up with as little as 1.5 mW from some of these products. For this reason, I chose the BTG-6-plus, because this particular product is guaranteed to be tested by Beam-of-Light to be between 4.5 and 5mW limit. Mine actually came with a hand-written sticker on it that said 4.92 mW. It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

The classic problem in 35mm film production was the video tap. Using a linear polarizer on a film camera with a video tap, could and often would cause the video feed to go dark because the partially silvered mirror in the video tap would get cross polarized. A very similar cross polarization is used to create Variable Neutral Density Filters with ND values between ND 0.6 (2 Stops) and ND 2.4 (8 stops). 8 stops means that only about 0.39% of the light gets past the filter. A Neutral Density Filter with an ND Value of ND 2.4 can be used to allow opening the aperture in a lens for shallow depth of field, or slow a shutter for various effects . . . it is not a good thing to do accidentally in an optical system with a mirror.

The next higher class, IIIb ranges from 5 to 500 mW. You can also legally purchase this class of laser in the United States. But there are restrictions on it's use, because these lasers are capable of permanently damaging vision. You can't use it in an environment where the beam could escape to the outside. To be explicit here, this means you can't legally use them outside. Now you may want to adopt a "no blood, no foul" attitude, and that's fine for you. But just know that if you ever make a mistake, or run into a narrow-minded individual, you don't have a legal leg to stand on - prepare for a good screwing. Furthermore, based on my own <5mW product, there is no reason outside of inferiority complex to get a higher power product for astronomical use. So how safe are these things (the sub-5mW class IIIa version)? They won't burn you. They won't cause permanent eye damage. Tests were performed on individuals who were scheduled to have an eye removed for medical reasons. For the purposes of the test, the eye was normally functioning. Test subjects stared directly at 5 mW lasers with there to-be-removed eye for five to fifteen minutes from various angles. No permanent eye damage occured. Some changes in tissue were noticed. Of course, in a real-world incident, laser light entering the eye would likely last for less than one second, as people naturally look away from bright things and close their eyes, so there is no real danger of direct damage. Having said that, these things are damn bright. If you hit a car driver at night with this, he'd be effectively blinded for at least a few seconds afterwards -- long enough to crash and die and have you go to prison for manslaughter. These are not toys for children. They should never be shined at people ever, and most especially not cars or planes. Finally, why green? Our eyes are most sensitive to green light. The same measured power output of a red laser would not produce a visible beam, because our eyes aren't as sensitive to red. By the time we could see a red laser, it would probably be reaching a dangerous level of intensity. BTG-6-plus Z-bolt offers several green laster pointers in the IIIa class. Note that these are often referred to as 5mW lasers, but they always have to be less. From everything I've read, there is a lot of variation in how much under 5mW the lasers are. I'm not sure how much to believe, but some claim that you can end up with as little as 1.5 mW from some of these products. For this reason, I chose the BTG-6-plus, because this particular product is guaranteed to be tested by Beam-of-Light to be between 4.5 and 5mW limit. Mine actually came with a hand-written sticker on it that said 4.92 mW. It also came in a very nice wooden box, and a pair of batteries. For my order, they were also giving away a free red laser pointer with it. I don't much care about this, but the free red laser pointer was packed into a second plastic foam case, which was much too big for the red laser pointer, but perfect for the green one. I don't know if they always give out this second case for the green pointer, but if you buy a pointer from them I suggest you ask them about it. The wooden box is very nice, but not very practical. The plastic foam case on the other hand is much more practical for slipping into your pocket or some luggage, and it provides nice protection. It closes with a flap that has two snaps in it, and it has slots for a spare pair of batteries. This is the case I'll be using whenever I'm carrying this pointer. So, how does my laser work? It works GREAT! Exactly as described - a green beam of light protrudes up and more or less stops right on the object you are pointing to. The end of the beam is a bit more blurry, and fades slightly, but it really seems to have an end where the beam essentially stops. It's extremly apparent what you are pointing to. I haven't yet tested to see how far away from me it remains visible, although people standing six feet away from me have been able to see it without a problem. What about light pollution? Many web sites say that in light-polluted conditions you won't see the beam, and you'll need more power. I suppose it depends on what they mean. The first time I used it, I was in a rural area, although not very far from the city, and there was a setting gibbous moon. Limiting magnitude was around 5.0, maybe 5.5. The laser was bright and easy to see. I've also used it in Cambridge Massachusetts, easily one of the most light-polluted cities on this planet. On the best moonless nights, limiting magnitude is 4.0. Again, the laser is easily visible, not quite bright, but not dim either. However, this only accounts for the light pollution - I was on a dark rooftop on a slight hill above other lights. So the light pollution was in place, but I had no lights in my eyes. If, by light pollution, you mean standing on a brightly lit street with a street light above you, then no, you won't see the beam. But if you mean, can you see it from a dark spot in the worst light-polluted sky imaginable? Yes, you can see it. Just for perspective, I used it about 45 minutes after sunset. The sky was still quite bright, with 20 minutes of nautical twilight left, and an hour of astronomical twilight. Limiting magnitude was perhaps 3.5. The beam was visible in these conditions. Dim, but unmistakably visible. These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email

CLASSIC FULL SOLE 100% SORBOTHANE® FULL LENGTH INSERT Classic Full Sole inserts are made of 100% Sorbothane® from heel to toe. The Classic absorbs shock and ...

Circular Polarizers contains a Linear Polarizer component that does the main work of polarization, as well as a second layer inside the filter called a Quarter Wave Plate, which “spins” the light after it goes through the linear layer and before it enters the camera lens.

These lasers are also supposed to work poorly in cold weather. I've used it in below-freezing temperatures. I was carefully to keep it in an inside pocket, or up my sleeve, when I wasn't using it. It worked fine. It tends to come on at less than full brightness, and then brighten up after a fraction of a second. Magic? So why DOES that beam of light simply stop at the target, instead of fading out in the distance, or seeming to go on "forever". Well, the answer's obvious if you do the math. If the laser is one foot away from my eyes, to the side, and I'm looking towards the "end" of the beam, then we can start to think in triangles, where the base is 1 foot long. If I look at a point 100 feet along the beam, then we have a tall skinny triangle with sides of 1 foot, 100 feet, The small angle for this triangle is 0.57 degrees. That's the angle between my sight line and the laser beam. But that means that the other angle is 89.42 degrees. The first 100 feet of beam covers 89.42 degrees of view to my eye. Let's look a thousand feet down the beam. We now cover 89.94 degrees of our field of view. Going ten times farther filled an additional 0.37 degrees of our field of view with a beam. At 10,000 feet, we get to 89.99 degrees - and we gained 0.05 degrees or three arcminutes. Beam-of-light technologies claims their beam from this product reaches 25,000 feet. If that's the case, then the additional 15,000 feet past what we just calculated will add 0.003 degrees to our view of the beam, or 10 arcSECONDS. The first 10,000 feet gives us a laser beam across almost 90 degrees of our view. And the next 15,000 feet of beam visually lengthens the visible beam by a size smaller than the disk of Saturn, Jupiter, or Venus. In other words, while the beam is fading out gradually, the part of it that we can actually see, the close part goes almost all the way to where we're pointing, while the long long section that fades out, adds almost no visible length to the beam. Even the section of the beam starting after one thousand feet away only lengthens the visible beam by the size of a crater on the moon that's too small to see with the naked eye. Where to buy? There are tons of people out there selling green lasers, and lots of horror stories. I chose Beam of Light Technologies because they've been in business for more than five years - I know this because I found a couple of negative reviews of them online from that long ago. But I found no recent bad reviews, and they were still in business. I'm perfectly satisfied with the product and with their service, although one could argue that when everything goes well, you haven't really tested their service. I apologize for writing in this space that Howie Glatter never answered my email. Apparently, spamassassin ate the email, and I found it later. By that time I'd already purchased my product. He has a good reputation, seems a bit pricy, but otherwise I can't comment on the quality of his products or services. Fine's Home Send Me Email