Detail depending on the depth of field and the selected step

[Igor]

Hi all. I immediately apologize for my English, as I communicate through Google translator. I am newbie. I have been reading the forum for several weeks, delving into and studying everything related to macro photography, looking at Alan's YouTube. I'm trying to do something, but so far I don't have everything I need, I can say I'm doing it "on my knee". I have some questions, I would be grateful if you could help me figure them out.

1. Specifications for microscope objectives (10x) indicate a depth of field of 3.5 microns. Do I understand correctly that for sharpness in the photo I need to take a step of no more than 3.5 microns, and even less than 70% is better, otherwise there will be gaps in the stack? Or can I do 10 micron increments?

2. I want to purchase such a lens: https://aliexpress.ru/item/100500229674 ... 9967754666 . I can’t figure out the size of the pixels on the matrix and how they affect sharpness. I have a Fujifilm X-H2 camera, the pixel size is (if I calculated correctly) 3.02 microns. Does it make sense to shoot at 10X magnification or I will not achieve the desired detail due to the small pixel size on the matrix. According to this forum post http://www.photomacrography.net/forum/v ... 13#p288313 the spot size would be 11.1 microns. It turns out that the spot on the matrix will take about 16 pixels and the image will not be sharp?

3. Tried stacking in "Zerene Stacker" and "Helicon", but the best ones come out in "Affinity Photo 2". On the forum, for some reason, I did not hear that someone folded it. Alan mentioned on YouTube that this program is not very good, but that was 3 years ago. Now it allows you to edit each image separately from a stack, like two other programs, adds up the same way as "Helicon" in 3 versions. Why is she bypassed?

4. Maybe someone else has tested such lenses from Aliexpress and will tell you if they are good or not, since the price for them is too tempting:

https://aliexpress.ru/item/100500409515 ... 0907903208

https://aliexpress.ru/item/100500558547 ... 3649521998

[BartMinnebo]

Hi,
1. that 10x objective would need you to make steps of 5µm or less for stacking without gaps

2. the 5x and 10x mitutoyo objectives have a resolution of 10µm on the sensor, so smallest detail on the fuji X-H2 would be 3 pixels in size, image quality will be fine.

3. Zerene and Helicon both were specialy developed for stacking and have been proven to give excellent results. One may prefer one over the others, but I find that's often very personal... Zerene tends to be prefered by those who want their to be as neutral as possible. I have never used Affinity so can't comment on that.

4. Those objectives might look like Mitutoyo clones, but could be completely different, no way to tell without trying.

Hope this helped

[Scarodactyl]

The chinese clones are highly variable and mostly not that good though some can be quite decent.

[rjlittlefield]

Igor, welcome to the forum. I am Rik Littlefield. I wrote Zerene Stacker, I have used Helicon Focus for almost 20 years, and I have spent a lot of time studying depth of field in theory and practice. With that background, I see your questions like this:

1a. That specification of 3.5 microns has an unusual meaning. It refers to acceptable deviation from perfect focus, so it is a sort of "one-sided" depth of field. Mitutoyo uses the same convention. But most other manufacturers and all the standard formulas refer to "two-sided" depth of field, because deviations on both sides of perfect focus are acceptable. If the AliExpress lens was specified as usual, the number for 10X NA 0.28 would be 7.0 microns. Multiplying that 7.0 microns by 70% gives 5 microns as a good focus step.

1b. However, that 70% number is only a sort of "fudge factor" that people have developed to compensate for issues that are hard to compute accurately. You should feel free to make that number bigger or smaller based on your own experiences.

2. At http://www.photomacrography.net/forum/v ... 13#p288313 , the post is confusing because it says "spot" when it really means "cycle" or "line pair". That is, the number refers to the total distance that is occupied by a bright spot and the dark space that separates it from the next bright spot. You need about 3 pixels per cycle to get a good capture. So, at 10 microns per cycle, and 3 microns per pixel, there is a good match between sensor and lens.

3. This morning I downloaded a copy of Affinity Photo 2.1.0, their latest version. I had hopes that it would be much better than previous versions, but that's not what I see. Both in the program and in the documentation for focus merging, I still see only one method, with no parameters that can be adjusted by the user. The results look quite good given that limitation. But I have no doubt that skilled users of Helicon Focus or Zerene Stacker could get better results for challenging stacks. (If I have overlooked something in Affinity Photo, like other methods or user-settable parameters, please let me know where to find them.)

4. I do not know if these exact lenses have been tested. Other inexpensive lenses that are "Mitutoyo style" have been tested before. At image center they gave results similar to Mitutoyo, but away from center the image was not so good. I have no reason to think that these are different. Still, given the low price some people may find them to be a good tradeoff.

--Rik

[Igor]

BartMinnebo, Scarodactyl, rjlittlefield, thank you very much for the advice and explanations, they helped me figure it out and make a decision!

If I have overlooked something in Affinity Photo, like other methods or user-settable parameters, please let me know where to find them.)

Rik, here in this video they say that stacking is done in three ways, and then they show how to retouch frame by frame: https://www.youtube.com/watch?v=HvMCUaGYNf8 .

I will study Zerene Stacker further, but so far the best results (very different) have been achieved precisely in "Affinity Photo 2", forgive me for these words, but I write as it is. Perhaps I just don't know much about Zerene Stacker yet and don't understand many of the settings, but "Affinity Photo 2" in automatic mode showed amazing stacking results.

The tube lens has no effect on NA, so it also has no effect on DOF. You can even change magnification by changing focal length of the tube lens, and still NA and DOF are not changed.

Rik, correct me if I'm wrong. As a tube, I want to use the lens "Canon ef 70-200mm" + adapter "Fringer EF-FX II Pro". If I set the focal length to 200 mm and put a 10X microscope objective, then the depth of field will be 7 microns. Now I want to reduce the focal length on the "Canon ef 70-200mm", for example, to 130 mm, in order to get a smaller zoom scale, then the depth of field will not change and also remain 7 microns? Or will it increase proportionally?

[rjlittlefield]

If I have overlooked something in Affinity Photo, like other methods or user-settable parameters, please let me know where to find them.)

Rik, here in this video they say that stacking is done in three ways, and then they show how to retouch frame by frame: https://www.youtube.com/watch?v=HvMCUaGYNf8 .

Thank you for the link. I watched that video before posting my first reply. I suspect you have been misled by a problem in language translation. The video does not say that stacking is done three ways. At 0:53, what the video says is exactly this:

Affinity Photo will take the set of images through three distinct processes. First images are all aligned. Then a depth map is created to guide the merging. And finally the most detailed areas of each image are merged together.

These three "processes" (1) align, (2) create depth map, and (3) merge images might better be called steps. They are indeed the same as the three main steps that Zerene Stacker uses in its DMap method, and that Helicon Focus uses in its Method B.

However, Zerene Stacker also provides a different method named PMax, which does not construct a depth map at all, and Helicon Focus provides two other methods which they call Method A and Method C. Another word for "method" here would be "algorithm". The operation of these methods or algorithms is controlled by several parameters that can be set by the user, and the choice of method/algorithm is made by the user. Different methods are provided because some subjects do best with one method and some with another. In contrast, Affinity seems to provide only one method, and no user adjustable settings.

so far the best results (very different) have been achieved precisely in "Affinity Photo 2", forgive me for these words, but I write as it is. Perhaps I just don't know much about Zerene Stacker yet and don't understand many of the settings, but "Affinity Photo 2" in automatic mode showed amazing stacking results. The final result is an image where the subject has front to back sharpness.

There is no need to apologize for this. Each of the tools has different default methods and settings. It seems that you have stacks that are well matched to Affinity Photo and are not well matched to the default methods and settings of Zerene Stacker and Helicon Focus. If you already have a license for Affinity Photo, and it gives good results for your stacks, then the obvious choice is to keep using it. At some point you may have stacks that Affinity Photo does not handle so well, and if that happens then that will be a good time to look for alternatives.

The tube lens has no effect on NA, so it also has no effect on DOF. You can even change magnification by changing focal length of the tube lens, and still NA and DOF are not changed.

Rik, correct me if I'm wrong. As a tube, I want to use the lens "Canon ef 70-200mm" + adapter "Fringer EF-FX II Pro". If I set the focal length to 200 mm and put a 10X microscope objective, then the depth of field will be 7 microns. Now I want to reduce the focal length on the "Canon ef 70-200mm", for example, to 130 mm, in order to get a smaller zoom scale, then the depth of field will not change and also remain 7 microns? Or will it increase proportionally?

There is a fine point. The depth of field will not change as long as the sensor and display system have enough resolution to capture all the information that is in the optical image. If you reduce the magnification to the point that the optical image is sharper than the sensor and display system, then DOF will increase with lower magnification. The exact amount that it will increase is difficult to calculate.

--Rik

[Igor]

At some point you may have stacks that Affinity Photo does not handle so well, and if that happens then that will be a good time to look for alternatives.

Thanks for the detailed explanation. Most likely later it will have to be done.

There is a fine point. The depth of field will not change as long as the sensor and display system have enough resolution to capture all the information that is in the optical image. If you reduce the magnification to the point that the optical image is sharper than the sensor and display system, then DOF will increase with lower magnification. The exact amount that it will increase is difficult to calculate.

Now it's clear, thanks!

[JKT]

Rik, correct me if I'm wrong. As a tube, I want to use the lens "Canon ef 70-200mm" + adapter "Fringer EF-FX II Pro". If I set the focal length to 200 mm and put a 10X microscope objective, then the depth of field will be 7 microns. Now I want to reduce the focal length on the "Canon ef 70-200mm", for example, to 130 mm, in order to get a smaller zoom scale, then the depth of field will not change and also remain 7 microns? Or will it increase proportionally?

Just a side note to your plans on using the zoom: That 130mm, which you mention, is pretty much the same as using the full 200mm on FF camera. That likely means that extreme corners become dark due to vignetting in the tube lens. Going smaller than that will just increase the dark area in the corners. That was the case with EF 70-200mm f/2.8 III and RF 70-200mm f/2.8. I haven't tried others. The lower limit without vignetting would likely be around 150 mm or so.

[Igor]

Just a side note to your plans on using the zoom: That 130mm, which you mention, is pretty much the same as using the full 200mm on FF camera. That likely means that extreme corners become dark due to vignetting in the tube lens. Going smaller than that will just increase the dark area in the corners. That was the case with EF 70-200mm f/2.8 III and RF 70-200mm f/2.8. I haven't tried others. The lower limit without vignetting would likely be around 150 mm or so.

Thank you for your comment. I have a 1.5 crop camera. I tried to use the Jupiter 37A (135 mm) lens through the M42 adapter with a 10X microscope lens - there was no vignetting.

[Scarodactyl]

Zoom lenses typically introduce their own special vignetting when moving away from max zoom that a prime lens of equivalent focal length would not.

[Igor]

Zoom lenses typically introduce their own special vignetting when moving away from max zoom that a prime lens of equivalent focal length would not.

Can adding macro rings to a tubular lens be considered a change in focal length?

[rjlittlefield]

Can adding macro rings to a tubular lens be considered a change in focal length?

It's not the same. Adding rings will move the rear lens away from infinity focus. That also changes the distance where the objective has to focus, and that change adds aberrations that degrade the image quality.

In contrast, changing the focal length of the rear lens, while leaving the rear lens focused at infinity, only changes the image size (and possibly vignettes).

--Rik

[Lou Jost]

Zoom lenses typically introduce their own special vignetting when moving away from max zoom that a prime lens of equivalent focal length would not.

Can adding macro rings to a tubular lens be considered a change in focal length?

Sometimes adding a little extension reduces the vignetting.

[Igor]

rjlittlefield, Лу Йост thank you for the clarification!
Tomorrow I'll try to find out, since my lens will come. If everything is ok, I'll take it. Does vignetting affect which microscope objective is used? I now have a cheap lens, I bought it on Aliexpress for testing, in order to understand whether macro photography will captivate or not. Captivated I bought this 10X with a working distance of 15.8 mm (I checked it, it’s true): https://aliexpress.ru/item/100500444023 ... 9188252250 . With it, there is no vignetting on the tube tube (fixed lens "Jupiter 37A" 135 mm). Now I want to buy this lens: https://aliexpress.ru/item/100500229674 ... 9967754666 . Is it possible that with him vignetting will be on the same tube tube?

[Igor]

And another question: does it make sense to take a more expensive lens as a tube lens? Choosing such a lens, I was guided by the MTF schedule, compared it with similar lenses. I chose two: "Sigma AF 70-200mm f/2.8 APO EX DG OS HSM" and "Canon EF 70-200mm f/4L USM". Their MTF schedules vary, with Sigma having a worse one. Subsequently, I compared photos from 2 of these lenses under equal conditions with the same parameters and the detailing of the Sigma, especially in the corners, is noticeably worse, and the contrast is also worse. Chromatic aberrations are almost on the same level, if only Canon has a little more of them, but this is if you look very closely at high magnification. At the same time, Canon is significantly cheaper, so the choice fell on it. But maybe it makes sense to buy an even cheaper lens if the tube lens does not affect the quality of chromatic aberrations and detail?