Solar eclipse, earthquake on same dayDid you feel the earthquake in Central Virginia last night? Epicenter north of Glen Allen

Lederer's word decoding moment resulted in the 34-letter word being defined as "Atoning for being educable through delicate beauty." That is some deep dung but seems to somewhat appropriately describe a solar eclipse.

LensMTF

What did I think about the solar eclipse? Well, I must admit, it was kind of cool, but it never got dark like I thought it might do. However, the sky around me had an eerie, golden hue. I snapped pictures around 3:18 p.m., the peak time in the Tri-Cities area when roughly 85% of the sun got blocked by the moon. The special sight that everyone insisted I see looked like a crescent moon who had paid big bucks for an awesome headshot.

According to the Petzval field curvature plot, the total field curvature from the center of the image (0 degrees) to the edge (9.4 degrees) is about 0.23 mm. We can measure the Petzval curvature on the corresponding through focus MTF chart by measuring the distance from the peak of the 0 degree line to the peak of the 9.4 degree line. These peaks as seen on the plot are about 0.15mm apart. The field curvature plot exaggerates the real field curvature by 150%! This is because Petzval field curvature plots rely on approximations.

I noticed a driver stop along River's Bend Boulevard, place his protective eyewear, and look up. My neighbor's friend watched it with a lens removed from a welding helmet. It was very tiny, so I hope he only used one eye at a time to view the solar eclipse.

CHESTER — My view of the solar eclipse on April 8 was uneventful. There was so much hype about it, I imagined there would be a lot more to it. It also could be that I'm just not into the cosmic scene like others. If my coworker Bill Atkinson hadn't shared a pair of protective glasses with me, more than likely, I would not have made arrangements to observe the celestial phenomenon.

MTF

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Now that you understand MTF, the next important concept is how refocusing a lens affects it. This is called the through focus MTF. It is important that you get this information from your optical engineer, because without it you could end up with an optical system that does not meet your needs.

f/# (pronounced “EFF number”) is the focal length of a lens divided by the diameter of the beam of light that enters it. If you’d like to learn more about that concept, head to this page. For a simple lens, such as the one pictured above, the diameter of the beam is the diameter of the lens. More complicated lenses, like those on digital cameras, often have an entering beam diameter that differs from the lens diameter. The lens above has a focal length that’s twice the diameter of the entering beam, so the f/# is 2. This is written as f/2 (pronounced EFF two).

The Petzval curvature plot doesn’t always differ significantly from the through focus MTF plot, but it’s always a good idea to specify the maximum allowable focal shift in MTF when designing a custom lens. This is because just specifying the Petzval curvature approximation may differ significantly from the real field curvature.

I remembered my boss man Jeff Schwaner suggested taking shadow shots. Thank goodness I had a backup plan to contribute one photo at least. On social media, I spotted some awesome solar eclipse pics taken by my friend Richie Blick in Berryville, Virginia. He kindly shared them with me to share with our readers. His cute 13-year-old dog Ginger looks adorable sporting solar eclipse glasses.

As before, the blue curve represents data from the image’s center, red from the edge, and green from in between. To get these curves, the user specifies a certain spatial frequency that’s commonly half to three fourths of the maximum. Then the user has the lens design software plot the variation of the MTF at this spatial frequency versus focus. The zero point is typically the “best focus” for the lens. The plot shows how fast the MTF falls off as the image plane moves from its optimal location.

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Why such a large word to describe the solar eclipse? Why not? With such a huge amount of media coverage about the rare occurrence, it deserves a glorious adjective. According to Wikipedia, in his book "Crazy English," Richard Lederer breaks down the meaning of the compound word which was a song and single from the 1964 Disney musical film "Mary Poppins."

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Some cultures believe the sun and moon are in a heated battle during an eclipse. However, after they resolve their conflict with each other, darkness goes away. So, "expiali" in the 14-syllable word is spot-on. The star and natural satellite make amends, acknowledge previous wrongdoings, and brighten the world once again.

Jul 26, 2023 — To calculate a magnification magnitude, divide the distance of the image created by the lens from the distance of the object to the lens.

modulation transfer function中文

Last night while shopping at CVS, a young man, desperately seeking solar eclipse glasses, shook his head after the clerk told him they did not have any. He had been to several stores trying to find a pair. He seemed determined, so I bet he scored some before he called it a night.

Let’s start by observing the blue line. On it we can see that the MTF peaks at around 0.06 units to the right of the “best focus” and drops off on either side. The dropoff is not symmetric, which is common for systems with spherical aberration. For more information on aberrations, click here. Assuming that an MTF of 0.2 is acceptable, the image plane can be moved about 0.4 units to the left of best focus or 0.16 units to the right before the resolution at the center of the image is no longer acceptable.

This morning, I asked my friend Robin Pruett to alert me when it was time to go outside and watch the moon pass between the Earth and the sun. After she called at 3:04 p.m., I grabbed my spectacle spectacles and raced outside to watch what was sure to be a supercalifragilisticexpialidocious sight in the sky, a moment to remember.

mtf是什么意思

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We can measure Petzval field curvature several different ways, but we prefer to rely on the through focus MTF plot. It generally gives the most accurate representation of the real field curvature. See the two plots below as an example. One is a plot of the through focus MTF and the other is a simple field curvature plot of the same lens. Both of these plots are for monochromatic light at 550nm.

Modulation transfer function

Now that you understand the theoretical limit of through focus MTF, it’s time to get practical. A picture of the through-focus MTF of a real lens is displayed below.

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The first basic principle of through-focus MTF is the geometrical limitation. Any lens that focuses light produces an “illumination cone.” See below for an example:

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The central spot is at the focus of the lens and the spots to the left and right correspond to the illumination cone before (to the left) and after (to the right) focus. As you can see, the spot size increases dramatically as you move away from focus. This forms an upper limit on the through focus MTF. The F# of the optical system will determine how fast this happens. Any photographers reading this may be familiar with this term, but let me explain it for the others.

Another neighbor who was sitting on the back of his truck tailgate, showed me his images. I showed him mine. We both agreed neither of ours were worthy of sharing. Ha! At least he had one with a jet passing the solar eclipse. Granted, it did look like a dot made with a blue ink pen. LOL! His girlfriend in Michigan joined in on our solar eclipse discussion. She said the eclipse cast a very large shadow where she lived.

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The spot size at a given distance from focus can never be smaller than the diameter calculated from the f/#. Take, for example, the f/2 lens shown above. The spot size 1 mm away from the focus can never be smaller than 1/2 mm. If the lens were f/2.5, the spot could be no smaller than 1/2.5 or 0.4 mm. Applying what we learned about MTF, the MTF at 2 cy/mm would be essentially zero for an f/2 lens 1 mm from focus. An f/2.5 lens would have a nonzero 2 cy/mm MTF at 1 mm from focus, but it would drop to zero at 1.25 mm from focus.

The lens you look through is called the ocular. The lens near the specimen being examined is called the objective. The objective lens is one of three or ...

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Unfortunately, the best focus for the light at the edge of the image (red) and even part way out (green) does not lie at the same place as it does for the center of the image. This condition, known as “field curvature”, is caused by one of two aberrations: Petzval curvature or astigmatism. See our Aberrations page to learn about these. Also, the sagittal and tangential curves do not peak at the same focal position. This is typical of astigmatism. However, the difference between the sagittal and tangential curves is much less than the difference between the center and edge of the image. This means your optical engineer would tell you that the Petzval curvature is more of a problem than the astigmatism. If you can’t get the entire image in focus at the same time, this is likely the problem. If you focus on the edge of the image, the center looks fuzzy (and vice versa) as seen here.

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In my apartment complex, a family of five, three young children and two adults, were on a third-floor balcony looking up at the sky. None of them were wearing glasses. Yikes! I hollered up at them, pointed to my flimsy glasses and shared with them, "You're supposed to wear a pair of these." They smiled, waved and resumed the hazardous moment in time. Hey, I tried.

Through-focus MTF can be used to determine the depth of focus for a lens. In the above plot, all three fields have an MTF above 0.2 from -0.14 units to +0.07 units. This means that the total depth of focus is 0.21 units. If the units are mm, this would be very easy for a mechanical designer to accommodate, but if the units are microns, it would be exceedingly difficult. That’s why it’s important for your optical engineer to communicate this information to you as you design your optical system.

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The next total solar eclipses in North America are not anticipated until 2044 and 2045. If you missed this one, I bet you will find enough 2024 solar eclipse images and videos online to keep you busy until then.

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The light from the lens comes to a focus and then expands again, as it should. The diameter of the illumination cone (called the spot size) is very small at the focus but it is larger at either side. The following figure, called a “through focus spot diagram”, shows its variation on either side of focus.

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