Damage to image sensor with long exposure

Quote from: Skyfox on 02 / July / 2011, 15:43:43

Hi all, new member, first message post.

I have the Canon S5 IS and a memory card running CHDK 0.9.9-915 v101b. I'm wondering about causing damage to the image sensor when using CHDK to make a very long exposure. One time I tried making a long exposure with the parameter set to the max 2048 seconds (over 34 minutes) with a 950nm IR filter in an attempt to make IR view photos. After that much time the screen seemed to show dead pixels but I never noticed them in actual photos. Since then the dead screen pixels seem to have returned to function so I don't know if it was the sensor, display screen, or something else like an effect of using an IR filter.

Just today when fiddling around with CHDK I noticed it could do a multiplier function on the shutter speed, up to 100 seconds with up to 100x multiplier for up to 10,000 seconds (2hours 46 min 40 sec) of exposure time. Something I'm interested in doing is astronomical photography with long exposures. My question is, at 2048 seconds or 10,000 seconds, is this length of exposure, even at very low light, safe for the image sensor? Or could it cause damage? And can the camera software even handle the amount of data from 10,000 seconds? I really don't want to ruin my camera.

First of all, ~2048 seconds is probably the absolute maximum at the moment, because the exposure time (in microseconds) wraps around to negative there. The fact that you can set larger values in the UI doesn't mean they can actually be used. Some cameras are known to produce bad images with shorter exposures.

Secondly, no one on this forum can give you a definitive answer as to what may damage the camera. Only Canons engineering department might have that information, and I don't think they will share. We can only report the results of our observations. As far as I know, no one has reported damage due to extremely long exposures (or any damage definitively linked to CHDK), but given the limited use for exposures that long, it's not out of the question.

Finally, I'd suggest that stacking multiple shorter exposures is likely to be better in pretty much every possible way.