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01-07-2019, 05:43 PM   #1
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my first beginners problem please help to bring my old 28mm lense to life

Ok so I have three old lenses I used to use on My ME super and am trying to use them on my K-70.


Firstly have the kit lens which came with it a Pentax 50mm 1.7 M works fine and so far reasonable results with just snapping and experimenting.


Tokina 70-210 which has a A setting and works fine


The one I'm trying to get to work is the Petri 28mm F2 Think its a Cosina clone just like the 50mm it has no A button however all my photos are black with this lens the aperture manually opens and all seems to work well on the lens. When I edit the pic I can bring up the image sometimes however I cannot get this one to take an image, any tips.

01-07-2019, 07:16 PM - 2 Likes   #2
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A quick thing to try is to switch to Av mode. The camera won't try to move the aperture blades at all, no matter where you set the aperture ring. So the lens should be wide open when you take a shot. The exposure won't be perfect but the shot is likely to be too bright.

A lot of the potential problems result in a shot that's too bright - not using M mode, oil on blades, etc. Are you sure that the blades manually open? They should act like the 50mm lens. Off-camera, set the aperture ring to f16 or f22 and you should see closed blades. Flick the lever on the mount and they should open quickly and snap shut when the lever is released. You can mount the lens and see the blades open back up as the lens is rotated. When the lens is locked in place, the blades are fully open. If that doesn't happen, the lever might be bent so that it doesn't engage with the camera. Compare it with the 50mm.
01-07-2019, 07:39 PM   #3
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QuoteOriginally posted by Just1MoreDave Quote
A quick thing to try is to switch to Av mode. The camera won't try to move the aperture blades at all, no matter where you set the aperture ring. So the lens should be wide open when you take a shot. The exposure won't be perfect but the shot is likely to be too bright.

A lot of the potential problems result in a shot that's too bright - not using M mode, oil on blades, etc. Are you sure that the blades manually open? They should act like the 50mm lens. Off-camera, set the aperture ring to f16 or f22 and you should see closed blades. Flick the lever on the mount and they should open quickly and snap shut when the lever is released. You can mount the lens and see the blades open back up as the lens is rotated. When the lens is locked in place, the blades are fully open. If that doesn't happen, the lever might be bent so that it doesn't engage with the camera. Compare it with the 50mm.
Thanks for the tip played about a bit with the leaver and it works have taken pics in P mode and working need to play with it to understand its best settings now
01-07-2019, 07:58 PM - 1 Like   #4
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In order to use lenses without "A" settings you should be using stop-down metering with the green button in manual mode.

Refer to the following:
How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - PentaxForums.com
Manual Metering on Pentax DSLRs with Manual and Automatic Lenses - PentaxForums.com

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