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01-22-2014, 06:43 AM   #1
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fixing a 35mm 2.8

Hi

ive got a 35mm 2.8 A lens. The rear mount of the lens that secures it to the camera isnt working. Ive tried replacing it with a rear mount off a 50mm f2 A lens, and the lens does attach to the camera and still works like and A lens but the aperture readings are all off. the camera reads f2 when the lens is on f2.8.

Ok so the point is I cant afford to get someone else to fix it and I cant find a rear lens mount for a A lens 2.8. So does anyone know if i can use a rear lens mount from a f2.8 M lens?

Will it still perform like an A lens

sorry if iv over complicated things

01-22-2014, 06:54 AM   #2
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What was wrong with the original mount?

The contacts that tell the camera what the aperture is are just a series of conductors or insulators. If you can't find the correct mount you need to make the ones on the replacement match the original.

http://www.robertstech.com/matrix.htm
01-22-2014, 07:18 AM   #3
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The M lens mount lacks the A contacts, so of you use that mount, your A should become an M.
01-22-2014, 09:33 AM   #4
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QuoteOriginally posted by elliott Quote
What was wrong with the original mount?

The contacts that tell the camera what the aperture is are just a series of conductors or insulators. If you can't find the correct mount you need to make the ones on the replacement match the original.

http://www.robertstech.com/matrix.htm
hey

in reply to what was wrong with the original mount?

part of one of the three teeth things which actually hold the lens in has partly chipped off. the lens will go into the camera but wont turn to click into place

01-22-2014, 11:54 AM   #5
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QuoteOriginally posted by cookiies Quote
hey

in reply to what was wrong with the original mount?

part of one of the three teeth things which actually hold the lens in has partly chipped off. the lens will go into the camera but wont turn to click into place
If you're into a bit of diy this is in principle very doable, refer to the previous post with the link to the KA mount contacts info. You need a replacement bayonet ideally from another pentax with the same screw holes and of the same thickness (otherwise the project multiplies in difficulty) then it's a matter of creating the same contact pattern and a hole to house the spring loaded 'A' contact.
This post may be helpful...
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/63878-how-c...s-ka-lens.html

There is also the mechanical connection that prompts the A contact to rise when the aperture ring is turned to 'A' position that might be more tricky to do..

Best of luck
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