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Is there a way to control the aperture of an EOS lens when it is not connected to a camera body?

New Contributor

I'd like to use a Canon EOS lens with an astronomical CCD camera to do some non-astronomical imaging.  This project requires the ability to change the lens aperture to deepen the field of view.  I've heard that the aperture can be set by connecting to an EOS body, hitting the DOF preview button, and detaching while keeping that button held down.  But we won't necessarily have an EOS body available while doing this testing.  I was wondering if there was any adapter that has the electronic inputs to control the aperture, of if such information is out there (like format of the necessary electrical signal, pinout info, etc.)  so that we could build our own controller.





Respected Contributor

Forum Elite

You need to get a hold of Tim Campbell on this forum.  He knows everything about how to do astro stuff with a Canon.


BTW, it would not be my first choice to try the solution you described on a EOS body.  I doubt it will work and may harm both!

EOS 1DX and 1D Mk IV and several lenses!