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02-20-2016, 10:51 PM   #1
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Deglassed AF kit zooms as helicoids?

Hi all;

As a possible future project I was thinking of deglassing a cheap AFkit lens (i.e.28-80, 35-70) to use as a macro-helicoid with auto aperture for projector lenses without diaphragms and reversed primes wide open. This is intended as a somewhat more user friendly option than bellows. I have some questions:

1) Has anyone out there tried this already? I've seen examples of people using deglassed Helios primes to use as helicoids, but have not seen this done with a zoom or AF lens. Is this idea totally nuts and wholly impractical?

2) Are there any lenses that might be a better prospect than others? I know it would probably be better to use one that extends in only one direction when zooming as opposed to the lenses that , like 18-55s, start longer, get shorter at around 24mm, then get longer again.

02-20-2016, 11:08 PM   #2
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I suspect the inner workings of zooms in general might make this a much harder project than though. An old prime sounds more practical to experiment upon. The focusing helicoil on a prime would still allow some modest degree of magnification adjustment. Deglassing old teleconverters is more common although you do end up with a fixed length extension.
02-21-2016, 12:29 AM   #3
dms
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Deglassed Vivitar macro 2x TC becomes a variable length tube, and if PKA it has A contacts as well. I have not done this with mine--but it is a beautifully made variable lengthTC.
02-21-2016, 01:42 AM   #4
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Try it

Once I removed one element from my broken Prinzflex 70-210mm zoom lens and it became a macro. Albeit a very limited use macro as it has incredibly short focusing disctance.

Failure in my copy meant it produced soft focused pictures until stepped down to f16-22, and when I made it macro I still had to step it down to let's say f8 for any sharpness.

This is a 1/20th sec. chronograph dial in my watch made with my Prinzflex Macro Mode Turbo GTI

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Last edited by sfkazimierczak; 02-21-2016 at 01:44 AM. Reason: typo
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