I was playing around with really long override exposures last night, and had the regular Canon shutter speed set to less than 1.3 seconds, which is the threshold for whether the camera does an auto dark frame subtraction. So it didn't do the noise removal afterward, and I noticed a lot more bad pixels in that image compared to others. For later pictures, I set the Canon shutter to more than 1.3'' so it would do the noise removal. I thought this was interesting, and maybe it's a good way to control whether or not the dark frame subtraction is performed. Has anybody else found that out already?
But are you sure the camera didn't do dark frame reduction (you can tell pretty easily because the camera takes twice the time to take the photo when it also shoots a dark frame)?
I'm asking because some cameras have more than one bad pixel list. The list it selects depends on (at least) exposure time. If this selection doesn't depend on the final, true (overrided) exposure time but instead on the exposure time selected by Canon (auto or manual) exposure, the result would be bad pixels in your situation (e.g. shooting a 5 second exposure using CHDK override when camera is set for 1/100 s exposure instead of a 5 second exposure).
I think that the Canon firmware's choice of bad pixel list is based only on the Canon shutter speed, based on the picture I took where Canon's was less than 1.3'' and CHDK's was something like 32''. For that reason, is it a good idea, when using shutter speed overrides, to have the CHDK bad pixel lists configured? Is CHDK's bad pixel removal done instead of, or in conjunction with Canon's bad pixel removal?
When the CHDK bad pixel removal feature (the one with the badpixel file - not the badpixel.bin for DNG creation) is enabled,the badpixels from your (CHDK) list will always be "corrected", additionally the Canon firmware always "removes" the bad pixels from the internal fw list.
Quote from: fe50 on 22 / August / 2009, 15:50:54When the CHDK bad pixel removal feature (the one with the badpixel file - not the badpixel.bin for DNG creation) is enabled,the badpixels from your (CHDK) list will always be "corrected", additionally the Canon firmware always "removes" the bad pixels from the internal fw list.Would the two lists have some overlap in them?
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