Is support for old Sigma lenses (400/5.6, 500/4.5) possible on 30D, 40D? - Feature Requests - CHDK Forum

Is support for old Sigma lenses (400/5.6, 500/4.5) possible on 30D, 40D?

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I've got two Sigma lenses that aren't fully compatible with new Canon cameras, a 400/5.6 apo tele macro and a 500/4.5 apo. On my 30D and 40D only Av and M mode is possible with these lenses fully open (aperture f/5.6 and f/4.5 respectively). Any time the camera needs to adjust the aperture the camera freezes into an ERR01, claiming the lens contacts may be dirty. According to a Sigma technician the camera, when closing the aperture, expects a fast confirmation from the lens saying the aperture is closed as ordered. These lenses (and several others) are too slow in responding, causing the ERR01. Some lenses could be rechipped by Sigma with faster chips, avoiding this problem. Consensus on the net is that starting from the 10D, Canon changed the protocol, causing this problem. D60, 1D, 1Ds should be fine, and according to one source the 400D as well (haven't tested this, all I know, all the cameras I tried (300D, 30D, 40D, 450D 1000D, 5D) did not function).

Anyway, my question is: would it be possible to disable the aperture closing check in a modified firmware, thus enabling full aperture use with these lenses?   


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