Enhancing sharpness and resolution with objective, how to set up

[andedk]

I have been happily using the Zerene Stacker system and stackshot rail system for over 10 years now. It is a fantastic system! Despite a lot of experimentation with my camera equipment/lens, I have not been able to solve my focus issue.

My photos are relatively good, but I really would like to learn how to create a sharply focused image of my fossil teeth. The teeth are about 2 x 1.8 mm on the occlusal surface and have crenulations and cuspules, thus DOF is definitely an issue. I was hoping that stacking images would solve the focus issue, but it did not. I use a Canon EOS 7D with a Canon MP-E 65 mm magnifying macro lens.
I have done a lot of experimentation with distance from the camera back (used extension tubes), zoomed photos vs. not zoomed, changed ISO settings, F stops, number of steps for the rail system. No luck getting a crisp, focused, stacked image.

One colleague suggested using the Mitutoyo M Plan Apo objective. I think this is a good idea. What equipment do I need and how does one set this up?

I am attaching the best images I have so you can see that I am so close to having clearly focused images, but not quite there.
Thank you for any ideas you might have.

[Adalbert]

Hello,
Welcome to the forum!
Yes, please show your photos.
Best , ADi

[rjlittlefield]

andedk, welcome to posting!

I received your note about difficulty posting images. Instructions for posting can be read at viewtopic.php?f=20&t=41917 , "Image hosting procedures: the short story". Note especially the limit of 1024 pixels on width and height, in addition to the 300 KB limitation on file length.

But I am happy to post here the two images that you sent me by email:

These images look like a good start as they are. I expect they could benefit from digital sharpening. In this size range, images fresh from the camera are always softened by diffraction in the optics. To recover maximum visible detail requires digital sharpening at a level that would reduce a landscape photo to trash. For scientific work I recommend using some neutral method such as "Unsharp Mask" to avoid any potential of introducing artifacts by the newer AI-based smart filters.

That said, you could definitely get sharper and more detailed images by using a different lens. The MP-E 65 is an excellent lens for some purposes, but for your purposes a microscope objective would work better. A good 10X microscope objective can be "pushed down" to slightly lower magnification so as to fit an entire 2 x 1.8 mm onto your EOS 7D sensor (22.3 x 14.9 mm), and I'm thinking that's the way to go. The key parameter for sharpness & resolution is something called "numerical aperture". This is quoted directly for microscope objectives, with the abbreviation "NA". Typical values for a 10X objective are in the range of NA 0.25 to 0.30. But even the best sample of MP-E 65, one that is sharpest wide open, corresponds to only about NA 0.15. Maximum achievable sharpness & resolution increase in direct proportion to NA, so you can see there's quite some opportunity for improvement in going from NA 0.15 to say NA 0.28, which is the value for the Mitutoyo M Plan Apo objective that is considered the "gold standard" at PMN.

In addition to the lens, illumination can have some effect on sharpness. Perhaps contrary to intuition, the best sharpness is often achieved by using very "flat" highly diffused illumination. But this depends heavily on the subject, so experimentation would be required to know what works best with your fossils.

There are a couple of different ways of using the Mitutoyo. It is an "infinite" design, designed to be used in conjunction with another lens that finishes the image formation. The other lens can be either an ordinary telephoto lens, or a DIY or purchased "tube lens" assembly involving extension tubes or bellows. For general information see viewtopic.php?f=29&t=12147, "FAQ: How can I hook a microscope objective to my camera?". An example of the DIY tube lens assembly is discussed at viewtopic.php?t=35350 , "Raynox DCR-150 tube assembly with flocking". Functionally similar assemblies, mounted on rails for easy mounting on your StackShot, can be purchased from WeMacro or MJKZZ, as discussed on later pages in that same long thread.

I hope this helps. I look forward to further input from other people, and further questions from you.

--Rik

[soldevilla]

I agree, the MP65 is like a Swiss Army knife. It is a great, very versatile device, but it does not have the best knife or the best screwdriver in the world, each element is always better separately. Try a simple x4 microscope lens with extension tubes and you'll get better results, sure.

[Marcepstein]

Ive actually had some excellent results with the MP-e65, especially around 2-3x. And I have had some less than desirable results with it as well. Also Ive had good results with sharpening and denoising with Topaz AI ... some amazing results by the way, but also some that were not so good, and unwanted changes were made. Its like other programs .... some work and some work better. Im sendiing the makers feedback But there are images where Topaz A1 nails it for sure. There are some parts of Topaz that wont work on some images as it does make unwanted changes The technology is getting better. They are listening to customers feedback, So dont toss the baby just out yet.

[JKT]

Ive actually had some excellent results with the MP-e65, especially around 2-3x.

There's nothing wrong with it 1-2x either. On the other hand, 5x on APS-C is clearly too much for it. 5x on 24 MP full frame seems somewhat soft, but acceptable. Everyone has different sharpness limits, though.