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Photography Question 
Serina L. 

Can you reverse mount adapters?

I've seen many mount adapters that allow you to use Pentax M42 mount lenses on a Canon FD body but not the other way around. Can I use it in reverse and attach Fd mount lenses to a Pentax M42 body?

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12/4/2007 10:35:45 AM

Jon Close
BetterPhoto Member Since: 5/18/2000
  No, the adapters cannot be reversed. They only work one way - specific lens mount on one side, specific camera fitting on the other.

It is easier to adapt many lenses to Canon FD and EOS that the other way around. The reason is the Canon mounts are wider and closer to the film/sensor than other camera mounts. So other lenses can fit within the mount and be at the correct distance from the film/sensor to maintain infinity focus. Going the other way, a Canon lens on say a Pentax camera would be wider than the M42 or K mount, and because it would be farther from the film/sensor than it was designed, infinity focus would be lost, or require optical elements (acting as light-robbing teleconverter) to restore.

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12/4/2007 1:30:05 PM

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