Lens Mount Interlock

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Tom Schum
Tom Schum Forum Pro • Posts: 12,065
Lens Mount Interlock
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In recent threads and in some lens adapter reviews I've read online, there is mention of something different about the lens mount in L mount cameras.

I explored this with my Sigma fp L, and if you have a different brand and your lens mount behaves differently please post!

NO LENS: Camera works fine, LCD shows light hitting sensor and you can take a picture of that (not that anyone would want to of course).

L MOUNT MANUAL LENS: Same as no lens except that there is an image. Manual lens has no electronic contacts.

ADAPTED MANUAL LENS: Same as no lens and manual lens above.

PRESSING THE LENS LOCK BUTTON AT ANY TIME: LCD goes dark, camera operation is inhibited.

L MOUNT ELECTRONIC LENS: Pressing the lock button with the lens properly mounted will remove power from the lens, and the LCD goes dark, camera operation is inhibited.

LENS HALFWAY ON, BUT NOT LOCKED: LCD is dark, camera operation is inhibited.

Conclusions: (1) This supports electronic lenses by removing power from the lens when the lens is not properly seated and locked, and when you are changing a lens with the camera powered up. (2) A lens or adapter that does not fit properly will not lock properly and the lens lock button will not pop up, keeping camera operation inhibited.

How I tested for power removal:  My Sigma 45mm F2.8 DG DN lens has the aperture completely closed down to F22 when the lens is not installed on the camera.  When I power up the camera with this lens installed, the aperture opens up.  When I press the lens lock button, the aperture immediately closes down to F22 and camera operation is inhibited.  When I release the lens lock button, the button pops up because the lens is still properly seated, and the lens initializes, the aperture opens up, and camera operation resumes.

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Tom Schum
"Beware of taking advice from anonymous wise men." Quote from Anon.

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