Canon EOS 400D (EOS Digital Rebel XTi) Dark Noise Tests

This page allows you to view raw histograms of dark frames shot at 1/100s with all possible ISO settings of the Canon EOS 400D. Move your mouse over the list of ISO sensitivities on the left to view the corresponding histogram. You can get the original file (csv) with the histogram data by clicking the link. If you want to know how these were made see the original rawhistogram page.

The graph below represents the signal/noise ratio as a function of ISO speed. If you prefer dB units to "counts" move your mouse over the image. Since this is a ratio of maximum signal to dark noise it essentially represents the dynamic range of the camera. Keep in mind that there are other sources of noise in addition to the dark noise measured here. A Google query should give you some quite good introductory information. And interesting observation is that at ISO 100 and ISO 200 the 400D (Digital Rebel XTi) is better than the 30D, but the 30D is much better at higher sensitivities. I am even thinking of repeating my 30D test just to verify this. The EOS 1D Mark III on the other hand is much better then both the 30D and 400D.

The values were calculated as follows:


SNcounts = (2^14 - Mean)/Sd

SNdB = 20 * log(SNcounts)

Where "Mean" is the mean of the histogram (very close to 256 for all ISOs) and "Sd" is the standard deviation - which is what increases with noise.