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06-12-2021, 12:56 PM   #1
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Pentax 645Z Lenses on Film 645?

Has anyone used the Pentax 645 HD 35mm F3.5 AL, D FA 645 55mm f/2.8 AL SDM AW or FA 90mm F2.8 ED AW SR lenses on a Pentax 645 film body? Any samples you can share?

06-19-2021, 02:17 AM   #2
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I believe they will cover the film image circle but I don't think they'll AF.
06-21-2021, 03:46 AM   #3
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If it's the 645 then it will be manual focus. I'm not sure how you could change the aperture on the 90 or the 55. If you have the 645N then the DFA 35 will autofocus.
06-21-2021, 03:59 AM - 1 Like   #4
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If the lenses lack an aperture ring then the aperture can be changed on the camera, at least with the original 645 camera. It's the same as having the aperture ring in the A position.

06-21-2021, 08:14 AM   #5
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QuoteOriginally posted by Jonathan Mac Quote
If the lenses lack an aperture ring then the aperture can be changed on the camera, at least with the original 645 camera. It's the same as having the aperture ring in the A position.
Thanks. I've been trying to cut out a block of time to test 90mm focus by the 645N, but haven't succeeded so far. If the 645 can control aperture on the 90mm, then perhaps it can control focus too.

I am unaware of a Pentax lens guide that covers camera compatibility for all of their 645 DA and DFA lenses. (At the moment I can't find my copies of extant lens guides to confirm this.)
06-21-2021, 11:08 AM - 1 Like   #6
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The original 645 isn't auto focus, so won't be able to focus then lens, I shouldn't think as it won't have any mechanism to drive the focussing motor in the lens.
06-21-2021, 05:58 PM   #7
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OK, with the 645N, there is a mechanical focus drive on the camera, but none on the 90mm. The camera body lacks any user interface to change focus. There is an AF slider on the camera body, but it seems to be intended to determine whether the focus is point-like or more broad. Electrical focus is not implemented, or at least there was no attempt to focus in AF mode on the 90mm lens. I was operating the 645N with the special back for function testing without film. I am unclear whether the 645N can control the 90mm aperture. There is no 'P' mode, and 'A' mode expects the aperture to be manually set.

On the other hand, when testing the 75mm lens assembly, with the AF/MF switch on the 75mm lens body switched to AF, the lens focused as expected when the shutter button was slightly depressed. The 75mm, like the 120mm Macro, has the mechanical drive interface at the mounting flange.

So the 90mm will have to be manually focused for use on the pre-digital camera bodies, unless the 645NII has some added interface features. Aperture setting may not be possible. There is no thumb wheel or other interface on the 'N' camera body to set the aperture. I'm going to take a wild guess and suggest that external manual mechanical aperture setting on an SR (shake reduction) lens might have implications for design that were deemed worth avoiding.

06-22-2021, 12:51 AM   #8
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In-lens focus motors came to Pentax some time after screw-drive focus did. On K-mount SLRs I don't think they'll work on anything earlier than a K10D, so it makes sense that the 645 mount would also lack the ability to use in-lens focus motors even on early AF cameras.
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