The Best Magnifying Glass (or Magnifiers) for Reading - high quality magnifying glass

 2024-09-16 15:34:56

It becomes confusing because people think of a lens as a black round tube that goes on a camera. However, the f-ratio is found on any piece of concave or convex piece of glass. A lens, as a piece of glass, doesn't have f-stops. This is usually the front element of a camera lens. To this other complicated groups of concave and/or convex "lenses" are added to create a camera lens.. Some way is needed to reduce the amount of light going to the film or sensor. This is f-stops and is another element in a camera lens. Natural f-stops are either half or double the one before or after it because they let in half or twice the amount of light to the sensor.

This is not exactly correct. There is a difference between the f-ratio (F number?) and a f-stop. The f-ratio (F number) is a ratio of the lens diameter and its focus point. An f-stop is a number dealing with light. If I read you correctly and understand what you were trying to say.

As an email subscriber you will receive exclusive in-store offers, online-only coupons, and helpful project tips and advice.

Every lens should have its' maximum aperture printed on it somewhere. Sometimes you will see the aperture described as a ratio, Instead of seeing " f/4 ", you might see " 1:4 ". Apertures can be set to narrower sizes than maximum, which is also known as "stopping down" the aperture.

Aperture describes a ratio of certain physical dimensions within the lens.. The aperture values that you see in the model number is the widest aperture setting that the can provide. The smaller the number, the smaller the ratio, which means the wider the aperture.

202019 — (a) define magnification by a spherical mirror and express it in term of object distance and image distance for the mirror. (b) the ...

on my amature DSLR camera that has lens 18-55mm f1.5-5.6 when using aperture priority, I can set the f-stop to f/22 for instance. Why? I thought the max value is f/5.6

AllenWrench Set

Your less expensive EF-S 18-55mm f/3.5-5.6 lens is named that way because at 18mm, the smallest f-stop is f/3.5 and at 55mm, the smallest f-stop is f/5.6. At 18mm, that lens has an f-stop range of f/3.5 to f/22 and at 55mm, that lens has an f-stop range of f/5.6 to f/38. The first f-stop in the lens name corresponds to the minimum focal length of that zoom lens and the second f-stop in the lens name corresponds to the longest focal length for that lens. This is more commonly known as a variable aperture lens.

The NA of a lens is directly tied to its working distance (that is an explanation for another time), so a stereo microscope lens, with its inherently greater ...

Apr 18, 2024 — Conclusion. In summary, a long pass filter selectively shorts wavelengths longer than its cutoff wavelength to pass, thereby effectively ...

A constant aperture zoom does not change the maximum available aperture as you zoom from one end of the range to the other end of the zoom range.

Allenkey screw

A Fresnel light is a highly versatile and controllable light that can be used as both a spot and a flood. Here's what you need to know about it.

This means that a larger hole will have a small F number and a small hole will have a large F number. So for instance an f4.0 lens is description of it's largest opening and if you adjust this to smaller opening then the f number will get bigger.

AllenWrench Socket Set

Above picture I obtained from snapshot.canon-asia.com. As you can see the author took the picture are f/9 while the lens itself has a max aperture of f/4.

Our True Value stores are independently owned and operated. Enter your City & State or zip code to see stores near you. You can use the format: [City, State] or [zip code]

Let's say you have a "lens", a piece of glass, 25mm diameter and it had a focal length of 100mm then the focal ratio would be f4 because 100 ÷ 25 = 4 (a ratio). If you increase the focal length to 200mm but do not change the physical diameter size of the piece of glass "lens" size then it becomes 200 ÷ 4 = 8, now it's an f8 lens. This can never change. However, in the case of a camera lens, there are two types. One is called a prime lens and the other a zoom lens. A prime lens can not change its focal length I.E., a 50mm f1.8 prime lens is always a 50mm f1.8 lens. A zoom lens due to the addition of several more "lenses", pieces of glass, it can change its focal length. Unless special steps are taken the f-ratio will change as it zooms.

A common beginners misunderstanding. Think of aperture as meaning an opening or hole (which is what it is), this can be bigger or smaller, it cannot be higher or lower.

Allenkey size

Home Depotallenwrench Set

Most people think of a round black tube that goes on a camera as a "lens". OK, it is, but a lens is actually any piece of concave or convex piece of glass. No tube, no camera.

As we are attempting to explain the concept to a beginner I was trying to keep things simple. I could have provided a whole screen full of information showing the mathematical concepts, even going on to T stops but I doubt that the OP would have read it or even needed to understand all the technicalities.

No problem let's try another approach. Do you have a binocular at home that you use? It is just a lens. Just like your camera lens. It has a constant f-ratio of, let's say f4. However they do not have a means of reducing the amount of light coming into the binoculars and the amount that comes out for your eye to see. Now if your camera lens did not have that extra system, the aperture blades, it would work the same way.

Yes, the listed aperture is the "natural" aperture of the lens, the widest it can go. The lens also has a set of blades, called the aperture, that can "stop down" and artificially make the lens have a smaller aperture as required, to reduce the amount of light and increase the depth of field.

Hex Key

I am confused with the relationship between the constant aperture number found in some luxury lens and the f-stop/f-number that is shown in the camera itself. I do not understand how can the f-stop inside the camera can be set to bigger than the max value of the lens' aperture. For instance, lens like EF 24-105mm f/4 L, my understanding is the aperture is constant at f/4 regardless whether it is zooming or out. so my expectation when I look at the info through my viewfinder I should see f/4 all the time, but this is not the case. by why??

The Rebounder Training Ball is a half rugby ball with a flat base and is the same weight as a match ball, allowing players to pass against a wall without a ...

Sep 25, 2023 — Any focal length above 135mm full-frame equivalent is considered telephoto. However, 70 to 135mm (full-frame equivalent) is considered short or ...

There are two different points here. Did you mention what lens you are talking about? It really doesn't matter but let's assume it was a ef 24-105mm f4L (constant aperture) zoom. When you zoom any lens, say, from 24mm to 105mm you change the focal length and therefore you change the f-ratio. Some lenses do not have special internal systems to cope with this so their f-ratio changes. An example might be the ef-s 55-250mm f4-5.6. However, a lens like the ef 24-105mm f4L has internal lens groups to correct for this and its f-ratio remains constant.

Consider this, as we wrap this up and I hope I made it more clear for you, all prime lenses are constant aperture lenses. Zoom lenses can be either constant or variable aperture but both still have the aperture system to adjust light coming in and going out. Two, there is nothing inherently better in a constant aperture zoom lens over a variable aperture zoom lens. And, the down side is cost and weight because they need that extra lens grouping inside to keep the f-ratio constant. Plus they generally are faster lenses and that costs more.

OK, now where you are losing it, is light. Cameras can shoot in a various levels of brightness and dark. Since we already established a lens can not change it f-ratio, how do we deal with that? We add a system of reducing the light that the lens can transmit. These are called f-stops. And, long way around, this is what you see when you look at the LCD or editing software and it tells you it was shot at f9, in you example. Your lens never changed but it reduced the amount of light it let the camera see.

Sometimes you will see the aperture expressed on a zoom lens as two values like the EF-S 18-55mm f/3.5-5.6 IS STM. This means that the maximum aperture changes as you zoom from 18mm to 55mm. At 18mm, the maximum aperture can be set as wide as f/3.5. When you are zoomed out to 55mm, the maximum setting is only f/5.6.

If you are using a shooting mode that allows the camera to select an f-stop for you, then the camera may select larger f-stops for your lens in brighter scenes like outdoors on a sunny day. This is why you may see a photograph with f/9 on the EF 24-105mm f/4L IS USM in your sample picture or an f-stop of f/22 on the EF-S 18-55mm.

I agree it is best to do small chunks at first but 'clear' chunks, at the same time. I know you and I don't have a problem understanding what we are talking about. A lens as a piece of glass has an f-ratio and f-stop. But people don't think of a piece of glass as a lens. They think of a black round thing that goes on a camera. In this case the f-ratio and f-stop are two different things and/or, at least parts, of the black round thing.

AllenKey

Oct 7, 2021 — Condenser: Usually sits just above the iris diaphragm. Focuses light onto the specimen. Illuminator: The light source, which illuminates the ...

10x10 summerhouse double doors x1 long side window ... 13mm t&g cladding & 3"x2"cls smooth planed in roof, no cheap osb boards used! 1 ...

For Glenn, your EF 24-105mm f/4L IS USM has an f-stop range of f/4 to f/22. This entire range of f-stops is available at any focal length on that lens. The name of the lens only includes the smallest possible f-stop for the entire range of focal lengths the lens can cover. Since the EF 24-105mm f/4L IS USM can have an f-stop as small as f/4 throughout its entire focal length range, you only see one f-stop in its name.

TEA laser - Easy to make homemade/DIY laser. This is an easy to make laser called the TEA laser that uses parts from around the house or that you can find in ...

The screen of a rear projection TV set (RPTV) has two or three layers. The panel with a concentic circular panel, seen only if you look inside, is the fresnel ...

I understand your wish to be precise and commend you for it but I believe that sometimes too much information can hinder people who are just starting out.

allenwrench中文

"But it raised another question to me. The lens says F4 constant aperture and I paid a lot for that ... I am expecting it to stay constant at f4 :-)"

Now where you seem to jump the track is when we have to add exposure to this equation. All the pictures you take can not be shot at the constant f4. So, how do we solve this dilemma? We add an aperture system that has the ability to reduce the amount of light that hits the sensor. These are called f-stop numbers and although they sound like the same number as your constant aperture f4 lens they are not. Bottom line here is your constant f4 lens shot the scene at f4 just like Canon claimed but the camera told the lens aperture system to reduce the amount of light to f9 because that is what made a perfect exposure. If you removed the aperture system from your constant f4 lens, it would shoot all shots at f4 and some would be over exposed.

"I understand your wish to be precise and commend you for it but I believe that sometimes too much information can hinder people who are just starting out."