Mitakon 20mm f/2 super macro - anyone?

Joined
Jun 1, 2019
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Seattle WA
Can't find a single good review for this lens. Does anyone have it here? I guess tragic flaw of this lens is NOT having focus ring. You are also so close to subject that traditional flash sort of lighting won't work and Mitakon doesn't have tiny LED ring light for it (which makes me think it could be a fun little DIY project to make tiny LED ring). Mitakon lenses in general aren't epitomes of IQ but I would still like to hear any opinions from members.
 

archaeopteryx

Gambian sidling bush
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Feb 25, 2017
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I'm aware of four (well, technically five) lenses like this in the 4-5x range. I don't own any of them as numerous other options are more capable and often cost competitive. Common starting points for a manual 4x implementation are reversing a 50mm manual lens on a 200mm manual focus adapted lens, 4x finite microscope objectives, and 4x infinity objectives with a Raynox DCR-150 as a tube lens. If you want a conventional lens form factor I'd suggest considering the Laowa 25mm 2.5-5x f/2.8.

I guess tragic flaw of this lens is NOT having focus ring.
You won't find a lens in this category which does. The most common methods are worm drive focus rails or focusing helicoids. For depth of field autofocus bracketing with a coupled rear lens or a collecting focus stacks with linear motion controller is usually preferred. Coupled lenses also provide the equivalent of a focus ring.

You are also so close to subject that traditional flash sort of lighting won't work and Mitakon doesn't have tiny LED ring light for it.
Regular off camera flash will illuminate fine but the results usually aren't considered aesthetically pleasing. The general technique you're looking for is macro diffusion. Personally, I use a range of coupled lens combinations for autofocus bracketing under diffuse continuous lighting---often ambient and not uncommonly naturally diffused---from 0.8-9.4x and subject shadowing is seldom an issue given a reasonable choice for the front/reversed lens in the pair.
 
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Joined
Jun 1, 2019
Messages
200
Location
Seattle WA
Thanks for the detailed reply! I probably asked this question too late. As it stands, I just got this lens home off of a Craigslist post :p Initial observations are exactly what I expected. Focal plane is thinner than any other lens I ever handled and without tripod/rail it is impossible to get sharp, in-focus picture. I used FL600R with diffuser, and you are right it does work, technically, but I am not liking it. I need another source of light or better placement.
Since I already got it, I will use it and post my observations here (a mini review sort of) in next few days. In case someone decides to buy it, I hope this will be helpful.
 

Robert Watcher

Mu-43 All-Pro
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May 2, 2010
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1,270
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El Salvador / Ontario, Canada
I found this fellows in-field lighting technique (on-camera flash using home-made diffuser to spread light down into the subject) for macro subjects, quite interesting:


I have just purchased a used Olympus 35mm macro lens in an effort to have some different results than what I have achieved with my traditional lenses. When I get back to Canada next week and have a chance to attach the lens to my camera - I am looking forward to see the results that can be had with such a simple diffuser for the lighting. While not of the magnification magnitude of the lens you are describing, the 35mm macro as well requires short distances between lens element and subject to get full macro ability, making lighting more of a challenge.
 

archaeopteryx

Gambian sidling bush
Joined
Feb 25, 2017
Messages
1,183
I just checked and the glass elements are smaller than US penny, that thing is one extension ring stacked on another and nothing much.
Pulling this over from the weekly purchase thread as more detail is perhaps interesting. The Yasuhara Nanoa 11mm, Mitakon 20mm, Laowa 25mm, and Canon MP-E 65mm all obtain magnification by extension (as do quite a few other similar lenses, such as the Olympus Auto-Macros). The bellows formulas for calculating the resulting magnification and effective aperture for exposure times are described in many, many, many places (e.g. Layton) but a succinct statement is
  • extension = f (M + 1) where f is the focal length and M the magnification
  • effective aperture EA = N (M + 1) where N is the marked aperture on the lens
Decreasing f therefore means a physically shorter lens for a given magnification. Which is why, for example, the Mitakon and Laowa are smaller than the MP-E. Downside is the corresponding decrease in working distance. Unless one starts to optically fancy things, which I don't think any of these lenses do.

Another limitation is these lenses are all f/2-2.8 so have maximum EAs near f/12-17 at 5x with corresponding limitation in image quality due to diffraction (though Yasuhara's specifications are a bit odd). It's possible to get 1-2 stops wider aperture with coupled lenses but more than that is difficult. It's a well known problem in microscopy.

Focal plane is thinner than any other lens I ever handled and without tripod/rail it is impossible to get sharp, in-focus picture.
Tens of microns (when wide open), yes. A regular photographic depth of field calculator will give something close, though the microscope equation will be a bit more accurate. Partly because it considers Abbe diffraction, partly because the assumption of constant numerical aperture which underlying bellows factor calculations starts to break down at short working distances.

I need another source of light or better placement.
Well, not quite exactly. But basically yes.
 
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