From: R. A. Greiner (ragreiner0_at_antispamdomain.not)
Date: Wed Jun 25 2003 - 17:06:09 EDT
I have done some preliminary testing and gathered data on a 10D dark frame study that I am doing. This data is on one camera and one data run. I have chosen to measure the older and poorer of the two 10Ds that I have. I have also use my own arbitrary settings and analysis. The camera was set to RAW, ISO1600. Captured frames were converted to 16 bit TIFF using the Canon Viewer. These were imported into Photoshop 6 and the histogram information taken from the photoshop results. Here are the results.
The first set of three darks were taken at intervals of 20 minutes or more. The camera was off until the time of the exposure and turned off between exposures.
Camera
Temp C Mean Median Std. Deviation
25.5 13.5 7 18.5 This is a bad very speckly dark (note it is a poor camera)
12.5 7.57 5 9.37 This is a fair dark but still quite speckly
6.0 6.0 5 5.06 This is a very, very nice looking dark speckles just visible
The following five darks were taken in sequence with the camera set for 4 minute exposures with a 1 minute waiting period between exposures. The camera was on all of the time of 25 minutes.
4.0 4.96 4 4.50 This is the best of the darks, very few visible specks
4.0 5.3 5 4.66 This is very, very good like the third one above
4.2 5.75 4 6.18 This one is very good, but clearly not as good as the last one
4.3 5.89 4 6.83 This one is good, but again clearly not as good as the last one
4.5 6.13 4 7.37 This is only good minus.
While the camera temperature was taken on the back of the body, it is clear that some warming of the camera is taking place. The camera dissipates 0.814 when resting and 2.74 watts while exposing. I do not know were in the camera the dissipation is taking place, but in the long run the entire camera body heats up to rise a few degrees above ambient. In this eaperiment the camera rose 5 degrees above ambient.
It is clear that the sequence of dark exposures deteriorates as the continuous sequency continues. I expect to try some sequences that are much longer when time permits. Sequences running two hours are not unreasonable. It appears at this time that the camera should rest between exposures. (preferably turned off completely)
It is clear that the appearance of the quality of the darks is highly correlated with the Mean value of the histogram. A small increase in the histogram gives a strikingly poorer looking dark frame.
The camera was a 0220 serial number range. I will next do these tests with a much better camera, my second and newer one. It is in the 0420 serial number range. While I do not find anything new in this data compared to the various posts on these issues. I think and hope I have started to quantize the issues.
It is clear that cooling the camera is a great help in reducing the dark noise.
[Non-text portions of this message have been removed]
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