Highest Resolution at About 2x

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

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ray_parkhurst
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Post by ray_parkhurst »

rjlittlefield wrote:That agrees nicely with the calculation that at lambda=0.55 microns, f/11.1 has a cutoff frequency nu_
0 = 0.1636 cycles per micron = 6.11 microns per cycle.
Rik...so would that mean that the "cutoff aperture" for 4.7um pixels is ~f17?

Miljenko
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Post by Miljenko »

Alligator, please wait for just a bit more. I'm just preparing 2x lens comparison that will follow shortly after 1x comparison which is ready for upload. I believe 2x will be online on Monday or Tuesday. There is a greatest surprise of all the magnifications. It's not a secret: Schneider-Kreuznach Componon-S 50mm f2.8. But there is a secret ingredient: a tube lens that turns this pretty average lens into a resolution monster...

Best.
Miljenko
All things are number - Pythagoras

rjlittlefield
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Post by rjlittlefield »

ray_parkhurst wrote:
rjlittlefield wrote:That agrees nicely with the calculation that at lambda=0.55 microns, f/11.1 has a cutoff frequency nu_
0 = 0.1636 cycles per micron = 6.11 microns per cycle.
Rik...so would that mean that the "cutoff aperture" for 4.7um pixels is ~f17?
Yes.

As crosschecks, I note that
1. https://www.microscopyu.com/tutorials/m ... resolution lists 4.6 um pixels for 10X NA 0.30 = f/16.7 (a theoretical calculation), and
2. my experimental tests at http://www.photomacrography.net/forum/v ... 164#101164 and http://www.photomacrography.net/forum/v ... 602#101602 end up concluding that
This illustrates what I've written elsewhere, that you would have to stop down somewhere between f/16 and f/22, to degrade the optical image to the same extent that a sharper image gets degraded by the 15 mpx sensor [=4.7um pixels, with AA and Bayer filters]. The nature of the falloff is different -- diffraction smoothly degrades contrast as detail becomes finer, while the digital sensor (including its anti-aliasing filter) tends to keep contrast high until it falls quickly at the end. But as shown in the images, the f/16 optical image clearly resolves a block or two beyond the camera image, while the f/22 image barely resolves (at very low contrast) the last block that is clearly resolved by the camera.
--Rik

elimoss
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Post by elimoss »

RobertOToole wrote:
When photographing wafers I cut a black mask with an approx. 24mm x 36mm cutout in the center to keep light from bouncing up to the lens. Seems to help with contrast.

Robert
Hi Robert,
Where exactly do you place the mask? Some distance between the lens and subject?

RobertOToole
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Post by RobertOToole »

elimoss wrote:
RobertOToole wrote:
When photographing wafers I cut a black mask with an approx. 24mm x 36mm cutout in the center to keep light from bouncing up to the lens. Seems to help with contrast.

Robert
Hi Robert,
Where exactly do you place the mask? Some distance between the lens and subject?
Sorry I didn't explain. I lay the material down on the wafer to stop light from bouncing back and creating flare. Sometimes it really makes a big difference in the blacks in the photo since it cuts glare.

Robert

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