4x lenses and objectives shootout

[Miljenko]

As I see it, 3x - 5x magnification could be the most popular photomacrography magnification range. There are so many possible solutions like microscope objectives, ordinary camera lenses and enlarger lenses, the ways you can hook them to your camera makes the number of outcomes close to endless. As a humble contribution to this community and the way to get answers to some doubts of my own, I have performed tiny 8-fold lens to objectives comparison. Optics included were:
Nikkor 20mm f/3.5 Ai (said to be pretty good at higher enlargements, thanks Damil)
Zeiss Flektogon 20mm f/2.8 (former Eastern Germany lens)
Nikkor AF 50mm f1.8 (cheap standard lens from my 1:1 shootout)
Schneider Componon-S 50mm f/2.8 enlarger lens
CnScope 4x ND 0.10 $25 microscope objective
Another Chinese 4x ND 0.10 objective from British Ebay seller
Leitz 4x ND 0.12 lent by forum member Emsiem (thanks Neno!)
Noname Chinese 10x ND 0.25 set to lowest magnification



At the back row you can see relay and extension devices; Nikkor 85mm f/2 Ai, 3 stage extension rings, Nikkor 200mm f/4 Ai and 150 mm bellows.
All shot using Nikon D7100 and Godox ML-150 macro ring flash in the dark with 2 sec exposure and second curtain sync, all the lenses reversed. Butterfly wing shot as 11 segment stack at 40 micrometer steps. All the lenses/objective were properly shaded and extensions/adapters covered in black matte finish.

In order to get as close as possible to 4x magnification, extensions were adjusted resulting by the following working distances (all measures in mm):



My first concern was the way I should connect the lens to the camera. I'm not sure I have ever read whether it's better via bellows or relay lens. So I have done it both ways. I believe I have found the answer once and for all (at least for those particular 3 lenses at 4x magnification):



Upper row using 85mm and 200mm lenses, lower with bellows/extension rings. Contrast difference is huge and disqualified extension way from the remaining tests.
Now we get to the main part. Here are center crops compared. No big differences actually, Leitz objective leading, with the Nikkor 20mm as the first runner up:



Important detail to point out is the optimal aperture: Componon and Nikkor 20mm did their best at f/4 while Nikkor 50mm and Zeiss peaked at f/5.6. Although I did my best to keep flash to object distance constant, slight variations resulted in different shades and detail presentation.
Differences extremely escalated when moving to the picture edges so at the corners it looks like this:


Again, differences are not huge IF the lens/objective is designed for this kind of image circle size. Three lenses performed terribly in this test: 10x ND 0.25 mounted directly to camera mount (approx. 4.5x magnification), Another 4x Chinese Objective and Leitz 4x 0.12. The first one was not expected to do any good since it was pushed way out it˙s design limits while Leitz is actually not an achromat,, requiring eyepiece compensation.

Your comments are very welcome!
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If your pictures are not good enough you are not close enough. - Robert Capa

[Greenfields]

Miljenko:

A very impressive and useful piece of work.

I cannot recall any other direct comparison between using reversed lenses on an extension tube and stacking the same lenses on telephoto primes. The improvement which using a prime makes is striking and consistent.

Henry.
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Feel free to edit my images.

[johan]

Excellent, very useful comparison, thank you.
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My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.

[emsiem]

Another educative and interesting test/review. Thanks Miljenko!
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Nenad

[rjlittlefield]

[Miljenko]

[Blame]

I am a little surprised too by the difference. I am an advocate of reversing onto primes but at 4x isn't that far away from what the componon-s 50/2.8 is designed to do. I guess it still isn't high enough.

I would expect huge improvements under 3x but only if the relay lens is up to it. I have found that some primes will do well but so far all I have tried vignette to some extent with a full frame camera (sony a900). For me, Enlarger lenses do better.

Judging by the dark corners I suspect vignetting. Could be the relay lens or too much distance between lenses. Won't be the Componon.

There is another interesting point. Your camera is a 24MP APS-c. Such high resolution is very much the way things are going but it does bring the advent of diffraction limits and empty magnification to lower effective apertures.

The Sony NEX-7 uses the same sensor so you can get a taste of the problem here .

What it shows is close on doubling of blur between f/8 and f/1 6. Given that the best of enlarger or camera lenses need to be stopped down to f/4 then even with a tube lens that is going to be f/8 effective at 2x. Much higher will result in empty magnification.

[Miljenko]

[fotoopa]

[Blame]

[Miljenko]

[fotoopa]

Thanks for the info!
Considering I still have to make the adapter I can install it as close as possible. You just need to be sure that you leave the lens in manual mode Since otherwise the front portion would come forward and press against the lens componon. I can still insert a soft rubber ring 1mm thick as protection. The next days I make an adapter on my lathe. Once the adapter is ready, I'll post a picture.

Frans.

[Blame]

There is one more thing you can consider to avoid vignetting when using a camera or enlarger lens as an objective and magnification is low.

You could try using both lenses wide open and put a stop between them. Just a circle of black paper with a hole in it.

Effective aperture =diameter of hole/focal length of relay lens.

It should have the effect of making life easier for the relay lens and harder for the objective lens but there is a fair chance of a net gain in image quality.

[Tim M]

[ray_parkhurst]

Deleted OT Post