35mm lens resolution measurements

alanrockwood · Jul 27, 2021

hoojammyflip said:
You can do this yourself nowadays with MTF Mapper. Sharpness is quantified by the MTF curves, which is the relationship between contrast and spatial frequency of an image. You need to be able to mount the lens on a digital camera body, and have a print shop print an A1 target and then mount this on a flat board. Its easy to do this wrong and have to start again.

https://sourceforge.net/projects/mtfmapper/files/windows/

A simple alternative is to print some text on a sheet of paper, with decreasing font size, and then see at what point the text is no longer readable with your lens. You can calculate the effective resolution limit from that. I guess the two methods will be correlated, but MTF Mapper does a whole lot more.

I went to the link you posted and read a little about mtfmapper. It looks like it uses the slant edge method that I wrote about in the post I made a few minutes ago.

bernard_L · Jul 27, 2021

alanrockwood said:
Jackson K.M. Roland has shown that the slant edge MTF method is not influenced much by noise or the contrast ratio of the image. Google his write up titled "A Study of Slanted-Edge MTF Stability and Repeatability". I think that one implication of this work is that it should be possible to print slant image targets on an ordinary inkjet printer and photograph those with a digital camera to determine the resolution of the lens on the camera.
(...)
ImageJ is a free program image processing program that has an MTF method available. I have used it, but I don't remember if it was a plug in or a built-in application.
(...)
I'm not going to try to discuss the magic that allows one to beat the Nyquist limit, but basically I believe it has something to do with the fact that imaging of the slant edge basically makes it possible to (conceptually speaking) interpolate between the sampling points without introducing aliasing, at least up to a point. The phrase "phase offsets" often pops up in discussions of this.

One does have to make sure that all digital sharpening schemes are turned of everywhere in the system. I think some digital cameras automatically apply some sharpening, which could be a problem.

Thank you for the reference to JKM Roland's paper. Note that the SPIE publication is behind a paywall, but on the imatest site it is freely accessible.
ImageJ is standalone; except of course for acquisition (digicam or scanner)
There is no confict with the Nyquist limit: with the slanted-edge method, one can obtain arbitrary fine sampling when the slanted edge is almost, but not quite perpendicular to the scanning direction. In round numbers, a 15° misalignment (wrt to perpendicular to scan direction) gives 4x oversampling, 7.5° 8x oversampling, etc, as long as the edge is indeed straight. That is the key point of the slanted-edge method. The wording "phase effects" in the article makes it sound more mysterious than it is. The slanted edge provides multiple scans of the edge, with small incremental offsets; merging the multiple scans results in a single scan with fine sampling;
Digital sharpening in the camera's firmware is not a problem per se: consider the camera as a black box (even if in silver finish) and consider that you are characterizing the system. Unless of course you want to characterize the lens rather than the lens+camera.

whojammyflip · Jul 27, 2021

alanrockwood said:
I went to the link you posted and read a little about mtfmapper. It looks like it uses the slant edge method that I wrote about in the post I made a few minutes ago.

https://flic.kr/p/2dNAoEj

MTF Pentax M 85mm 5.6 by hoojammyflip, on Flickr

Here is the Pentax M 85mm at f5.6. Its incredibly sharp in comparison to my other lenses. I am just showing this here as a means of quantifying.

Realistically, to get this detail, its on a tripod with cable release, to remove camera shake.

Edit: reading your post, contrary to the suggestion to print on A4, I would suggest following the MTF Mapper instructions: go to a specialist printing shop and get one of the MTF Mapper vector targets, and send to them for proper printing. Mount the print on a board, screw it to something solid. Its going to give you the same results as the Cicala testing. The advantage of Pentax lenses is that I can mount them on a digital body directly.

George Mann · Jul 27, 2021

Where is Henning when we need him.

Henning Serger · Aug 5, 2021

George Mann said:
Where is Henning when we need him.

.
Thanks George.

Well, he sometimes just need longer breaks from forums, to avoid a "forum burn-out"......And he has - fortunately - a real life outside the online-world, with lots of time-consuming challenges.
And he generally really prefers making photographs compared to talking about photography.........duckandhide...... And exactly that has been the case e.g. in the last days, concentrating on a wonderful photo project which gave me lots of joy, and resulted in 77 exposed films as well (and which of course are also now waiting to be processed by me).

I hope to come back here to this thread (and several others where photrio members have asked me to join in and share my knowledge) in the coming days / weeks. So please stay tuned.

Best regards,
Henning

flavio81 · Aug 8, 2021

btaylor said:
If you can’t get a great picture with any of the lenses made by the manufacturers listed above, the problem certainly isn’t your gear.

Yes, I think you're correct.

I don't feel anything missing when switching from Canon FD lenses to Nikkors to Pentaxes to Zenzanons or other lenses. The photographer is the weak link, not the lens.

Dismayed · Aug 8, 2021

wiltw said:
Gosh I would be happy if most folks understood the uses of

they're vs. there vs. their

so many cannot get a simple concept, 'contraction leaves out a letter or two...substitute an apostrophe'
So more complex concepts are hopeless.

It's just too complex to differentiate more than two things at once!

Dismayed · Aug 8, 2021

You know that your lenses are good when people who look at your photos ask about the camera that you used.

35mm lens resolution measurements

Privacy & Transparency

Privacy & Transparency