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Old April 10th, 2009, 03:27 AM   #1
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Disable aperture while having auto focus working..?

After gathering some quite helpful info from people on this forum (in particular by Jon Fairhurst), I set out to find a way to disable (with a punched plastic strip) some of the contacts on a 5D lens so its video mode wouldn't touch the aperture setting but yet would work for the auto focus control -- i.e., in my simple-minded assessment, I was hoping that one particular strip-contact would control the auto focus.

However, since I've decided to wait to buy a 5D until after the NAB show (10 more days), this exercise has been like learning to swim on dry land... and now, after gathering some lens schematics, I'm even afraid to get my feet wet. Just look at this diagram: http://photo.net/bboard/uploaded-fil...ad_id=24559084

Hence, my question remains -- will it be possible to just block out one (or some) of those strip connectors to disable the aperture while still having the auto focus working?

-- peer
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Old April 10th, 2009, 11:57 AM   #2
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Thanks, Peer,

You could try blocking only pin 5 or only pin 6, but I think I read that somebody else tried this, and they lost both auto focus and image stabilization.

It's worth another shot though.

Just make sure that your insulator can't come off and get lost in the camera. I did a tape experiment on a cheap lens - and the tape vanished. Not a good feeling!
Jon Fairhurst
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Old April 18th, 2009, 12:55 AM   #3
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Mylar correct?


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Old April 18th, 2009, 06:03 AM   #4
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It is not as simple as one pin that controls aperture, while another is used for auto-focus. Three of the pins carry SPI data communication to and from the body (and the data bit clock generated by the body). The lens sends its focal length, focal distance, model name, min/max aperture, and so on to the body in response to queries. The body can also send commands to adjust the aperture, control the focus motors, control the zoom motors (for the EF 35-80 PZ) and some things that I haven't figured out yet.

Some more details: Canon EF lens mount
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