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07-13-2015, 09:05 AM   #1
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Adaptor Questions Minolta to Pentax

I see there are Minolta to Pentax adaptors. They come with and or without glass. What is the difference and which is better? I also see multiple brands: if no glass is involved would it make a difference in the adaptor brand? With glass is there a standard? and again brand question as I see a variety of prices.

07-13-2015, 09:46 AM   #2
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I believe with glass keeps the focus range of the camera lens as printed on the lens barrel. Without glass would act like bellows, giving you a much closer focus but losing infinite focus? Im sure someone can clear this if erroneous. They probably dont really vary between brands especially the no glass option. Just a pair of unlike mounts assembled together with the minimal distance, or with lens correction.
07-13-2015, 10:14 AM   #3
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Minolta S (MD) mount had a focal flange distance of 43.5mm. K mount has a focal flange distance of 45.46mm. For a Minolta S lens to focus to infinity on a Pentax K body there has to be an optical correction. The non-corrected adapters are a short extension tube, the corrected adapters are a short tele-converter.

There are no adapters for Minolta (Sony) A mount lenses to Pentax K.
07-13-2015, 10:32 AM   #4
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All of the above is correct. If you go through the thread that boriscleto linked above you will find a brief review by myself of one of the glassless adapters. They have improved it somewhat since that review - enlarging the opening and some improvements to the Minolta side of the adapter.

Fotodiox used to have one that the glass could easily be removed by unscrewing a retaining ring and the lens but you still have the vignetting problem that I mention in the review. The adapters with the smaller opening will cut-off the image on full-frame sensors. The larger opening ones should be fine on FF.

The optical element will cause some degradation of the image quality. It is up to you if this is acceptable or not. If you have a large collection of lenses or some rarities like a 50mm f/1.2 or the vari-soft focus or shift lens you may find the loss of quality worth it just to be able to use these lenses on your Pentax.

If you have a collection of bellows and macro lenses definitely get the no-glass adapter. Some of the mirror telephoto lenses might work at infinity with the no-glass adapter but since I have none I can't say for sure.

Last edited by Not a Number; 07-13-2015 at 01:32 PM.

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