Large format macro tests

[Macro_Cosmos]

I'm not going to involve myself in the discussion of image quality as I understand that can be subjective at times.

Ray, you said you own a monochrome camera, right? Yes, that will remove any annoying debayering issues and greatly improve the purity, quality, and fidelity of images.
You then mentioned how you're not giving up on colour.

To me, the solution here is exactly that, giving up on colour. You can use the monochrome camera and do RGB blending. I actually gave this some thought. It's totally feasible and can be automated with the right parts and some time investment. This is commonly used in astrophotography as I'm sure many of us know already.

Workload in terms of images is tripled. However your end goal tells me it's worth it.
That said, your coin photos are all lower mag, parfocal RGB filters of that size is going to burn a massive hole in the wallet. A set of 52mm ones are like 4000 euros? I don't think parfocal is a requirement. With the right tolerance range, or some smart programming techniques on the stackshot, non-parfocal cheaper ones can be used.

[Pau]

That said, your coin photos are all lower mag, parfocal RGB filters of that size is going to burn a massive hole in the wallet. A set of 52mm ones are like 4000 euros? I don't think parfocal is a requirement. With the right tolerance range, or some smart programming techniques on the stackshot, non-parfocal cheaper ones can be used.

4000 for three flat filters?...it seems crazy
Could you link to this kind of filters?

If you are able to place the filters of the wheel into the infinite space between objective and tube lens it will avoid parfocality issues even if their thickness or RI are mismatched

[ray_parkhurst]

I think it would be better to take the discussion of monochrome cameras and techniques to another thread, but in answer to the question...no, I don't own a monochrome camera. I've been thinking about it but have not made the investment. I will start another thread and we can discuss monochrome there...

[rjlittlefield]

I knew that would be your next question. As the old adage goes, you don't know a subject until you teach it to others. The post above was the first time I've ever explained to anyone the historical context of the photos I'm making.

I am always pleased when my apparent denseness and persistent questioning turns out to have been helpful somehow.

Similar to other scientific endeavors, the traditional way die variety details have been presented for attribution purposes is through line drawings made by viewing the coin through a microscope. The relevant details are not extremely small, and indeed a practical maximum magnification is ~10x. This makes it possible for folks with hand loupes to view their coins and compare what they see to the drawings for attribution of the particular variety.

This description makes great sense to me, so I ran a little test.

It turns out that if I look at my high-resolution USAF 1951 test slide with my 10X loupe, and photograph it at 1X using my 36 megapixel Nikon D800E camera, the image resolves about 3 more sets of lines than I can see by eye+loupe. The last set that I can maybe resolve by eye+loupe, Group 5 Element 6 at 57 line pairs per mm, is too coarse to have even bothered to include in the sample images that I showed at viewtopic.php?p=163540#p163540 .

It's just one data point, with my eye, my loupe, and my camera equipment.

But perhaps some evaluation along these lines might be helpful while pursuing your newly clarified goals?

--Rik

[Macro_Cosmos]

4000 for three flat filters?...it seems crazy
Could you link to this kind of filters?

If you are able to place the filters of the wheel into the infinite space between objective and tube lens it will avoid parfocality issues even if their thickness or RI are mismatched

Didn't think about that, that's absolutely theoretically correct to me. Yes, the method I thought about indeed has the filters set within the infinity space. However, Ray's dealing with lower mag. I don't think he can exploit cheaper 1-inch filters.

I think I got mistaken with the price, anyway here are good Chroma rgbl filters. I've used their green one, good stuff. https://cn.chroma.com/products/sets/27101-lrgb
The $4000 comes from another discussion about astro.

Yes, the filter sets for monochrome can be killer, for 3nm Chroma 2" narrowband set (Ha, SII, OIII) its $4000! On top of the $8000 mono camera, crazy stuff!

That said, bigger rgbl filter sets are $2000. It's not 4000 but it's still an astronomical number for just filters. The Chroma set is $1000, that's better.
For us, OD6 is preferable, OD4 is a requirement, imo. Using low quality ones defeat the purpose of monochrome.

Cost depends on OD, $1500 for a 1-inch filter isn't uncommon: https://www.edmundoptics.com/f/ultra-na ... ers/37028/

[ray_parkhurst]

I knew that would be your next question. As the old adage goes, you don't know a subject until you teach it to others. The post above was the first time I've ever explained to anyone the historical context of the photos I'm making.

I am always pleased when my apparent denseness and persistent questioning turns out to have been helpful somehow.

Similar to other scientific endeavors, the traditional way die variety details have been presented for attribution purposes is through line drawings made by viewing the coin through a microscope. The relevant details are not extremely small, and indeed a practical maximum magnification is ~10x. This makes it possible for folks with hand loupes to view their coins and compare what they see to the drawings for attribution of the particular variety.

This description makes great sense to me, so I ran a little test.

It turns out that if I look at my high-resolution USAF 1951 test slide with my 10X loupe, and photograph it at 1X using my 36 megapixel Nikon D800E camera, the image resolves about 3 more sets of lines than I can see by eye+loupe. The last set that I can maybe resolve by eye+loupe, Group 5 Element 6 at 57 line pairs per mm, is too coarse to have even bothered to include in the sample images that I showed at viewtopic.php?p=163540#p163540 .

It's just one data point, with my eye, my loupe, and my camera equipment.

But perhaps some evaluation along these lines might be helpful while pursuing your newly clarified goals?

--Rik

While the historical context is useful to understand the application, I doubt I'd be satisfied with just resolving at what can be seen by eye with 10x loupe. The black and white photos from the 70's and 80's which replaced the hand-drawn guides pushed the resolution envelope forward quite a bit. Most recently folks have been taking decent quality images of their varieties for online sharing and publication, typically with USB microscopes but more and more commonly with more capable systems. Overlays of these images with reference images is the new standard method for proving attributions, so high quality references are needed. This requirement is difficult to quantify since the images being compared vary so much. However, I am more keenly aware now and will review the goals from the new perspective.