Where is the limit?

Images taken in a controlled environment or with a posed subject. All subject types.

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soldevilla
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Where is the limit?

Post by soldevilla »

I know it's been a while since I posted here. I hope to return shortly but I am busy photographing for books and articles and I can not show the images before publication.
I am receiving more and more requests to take photographs of smaller minerals. Increasingly smaller ... I am getting acceptable results in my Canon APS with FOV of 1.2mm maximum. From there, quality degrades a lot. I have a LWD x40 Nikon as a limit. I understand that at these increases the quality of the objective is very important.
But I do not see too many examples of microminerals photographed at that size, and I can not assess whether the problem is already the diffraction, the quality of my objectives, the vibrations of the camera (it is in Live View mode when I take the images), the low pass filters of the camera .... That's why I ask if someone has experience and has estimated the enlargement limit for "3D" objects. I see in microscopic photography with a lot of increases in flat preparations, but I do not know if the experience is adaptable to micro minerals.

Pau
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Post by Pau »

The main limitation is IMO the trade of NA vs working distance

Because NA is a function of the light angle entering the objective high NA can be achieved in most cases with very short working distance, not much problem for flat slides (in extreme cases like some 0.95NA dry or 1.4NA oil objectives even it is) but not workable for 3D subjects like your microminerals. Most LWD objectives have a wide frontal lens and a modest NA for this reason, for example 0.55 is very low NA for a 40X biological but usual for a 50X metallographic.

What magnification do you need? What final print size do you want?

So the main problem is diffraction blur because limited NA, all other issues are workable improving the setup. The sensor low pass filter doesn't seem the culprit if there is no problem at lower magnification.
Pau

rjlittlefield
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Post by rjlittlefield »

In recent images, I noticed http://www.photomacrography.net/forum/v ... hp?t=36752 as being possibly relevant to your interests. There have been other diatoms and forminifera photographed in reflected light that should be found by searching the forum.

Can you share any images that show your current limits and are the highest quality that your equipment makes? We don't know what your standards and requirements are, or any clue how you are doing already. But responding anyway...

For sharpness, the unavoidable limit is because of diffraction.

But any particular setup can also have additional problems because of vibration or deficient objectives.

At high magnifications longitudinal CA becomes a huge problem, see for example the 50X diamond abrasive plate at http://www.photomacrography.net/forum/v ... 9228#99228 . All of the Nikon objectives in my possession have this problem. The solution is to use apochromatic objectives like the Mitutoyo M Plan Apo.

And finally, at larger NA and especially with transparent crystals there is a worse problem with "haze" caused by out-of-focus light captured by the wider entrance cone. I don't know any great solution to this problem.

Given that your high mag objective is a 40X LWD Nikon, I strongly suggest to try a Mitutoyo M Plan Apo 50X NA 0.55. Assuming the Mitutoyo is in good condition, it will give a slightly sharper image with much less chromatic aberration and greater working distance which simplifies the illumination.

--Rik

soldevilla
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Post by soldevilla »

Pau wrote:What magnification do you need? What final print size do you want?
I think sometimes my friends are expecting the result of a SEM :D

Today I have tried to reach a 0.45mm FOV. with a horrible result, as I expected.

I try never to crop my image. And at the most are printed to a whole page. For exhibitions I print at 60x40cm. But the original image must be good, and I do not get it below 2mm or something less.
At high magnifications longitudinal CA becomes a huge problem, see for example the 50X diamond abrasive plate at http://www.photomacrography.net/forum/v ... 9228#99228 . All of the Nikon objectives in my possession have this problem. The solution is to use apochromatic objectives like the Mitutoyo M Plan Apo.
I know the problems of the chromatic aberration of the Nikon objectives, Rik. They disappear a lot if I work at the indicated distance of the finite objectives (210mm) but in return the definition loses. My comfortable space is to place the target from 1/2 to 2/3 of the distance. Mitutoyo is far of my pocket :(

I showed the image of 0.45mm of FOV and one that I consider acceptable to print, a bit under 2 millimeters of FOV

Image

Image

Beatsy
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Re: Where is the limit?

Post by Beatsy »

soldevilla wrote:.... That's why I ask if someone has experience and has estimated the enlargement limit for "3D" objects. I see in microscopic photography with a lot of increases in flat preparations, but I do not know if the experience is adaptable to micro minerals.
This isn't quite micro minerals, but they're made of silica and about at the limit I can resolve with my selection of optics. I used a 50x Mitutoyo M PlanAPO for this with hundreds of images in the stack - 1 micron steps. It can be taken further, but with a big step up in the accuracy required and much less room for lighting. I lust after the 80x high-NA objective that Charles K uses sometimes. Oly brand? I think it would handle these much better. Yum.

Image


soldevilla
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Post by soldevilla »

Thanks, Frederic. I know that you and a few others that I see on Facebook are capable of reaching resolutions like the ones I'm looking for. But I seek collaboration on how to reach that resolution and not that show me the differences that separate us. I've lived this for years in planetary photography, and it's frustrating to devote years of workflow and software testing, when I could have used that time to get more scientifically useful images. In astronomy I have already arrived where I wanted, but I do not know how much time I still have to devote to doing it in microphotography.

This is a recent image, and it is my limit. Sometimes I get slightly higher results and sometimes clearly lower results. It's amazing how lighting influences the final quality. It is taken with a Canon APS, and a finite Nikon x40 microscope lens placed at its recommended working distance, perhaps somewhat less. Perhaps a scrupulous cleaning of the lens can increase the acutancia reducing the flare, but it lacks definition in that image, and this is a reduced image.

Image

soldevilla
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Post by soldevilla »

I have used my astronomy software to reprocess the image. The deconvolutions are enormously powerful and I have to do some tests to find the optimal point without introducing processing artifacts, but it seems a good new line of research

Image

Lou Jost
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Post by Lou Jost »

Can you explain what you did? That is a nice improvement.

JH
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Post by JH »

Hi soldevilla

I like the picture but I think that the first of the two last pictures should be/look sharper with a Nikon M plan 40x - I have the 40x ELWD NA 0.5. Do you know if you have a vibration problem?

Best regards
Jörgen Hellberg
Jörgen Hellberg, my webbsite www.hellberg.photo

AlxndrBrg
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Post by AlxndrBrg »

That quality increase is astounding!

If that program/technique could be made available to the rest of us it would be great! Is it a proprietary thing, or something we can look forward to in the future?

Beatsy
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Post by Beatsy »

AlxndrBrg wrote:That quality increase is astounding!

If that program/technique could be made available to the rest of us it would be great! Is it a proprietary thing, or something we can look forward to in the future?
Pending soldevilla's response - "Raw Therapee" offers Richardson-Lucy deconvolution and it's free. Very good for sharpening and enhancing detail, but generally only if you use a radius less than one pixel. So you have to start with a reasonably sharp image - but the results can be astounding too (as above).

rjlittlefield
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Post by rjlittlefield »

See also the discussion about deconvolution compared to conventional sharpening, at http://www.photomacrography.net/forum/v ... 774#208774 and in the surrounding thread, and at http://www.photomacrography.net/forum/v ... 198#203198 which is linked in the other thread.

--Rik

soldevilla
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Post by soldevilla »

Jürgen. I have used the same tif from Zerene for the both process...

The soft is Astraimage. I have tried many deconvolution softs, but my knowledge of soft is very bad, and Astra is the friendliest (with reservations ...) that I have found.
As Beatsey says, I have to be very careful because it's a very powerful process, nothing like astronomy, where I have to squeeze the data down to the last detail. I have to learn now to control this so that the images do not look like children's drawings.

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