5D3 Pattern Noise Improvement and High ISO Cooking

Started Apr 1, 2012 | Discussions thread
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bclaff
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5D3 Pattern Noise Improvement and High ISO Cooking
Apr 1, 2012

Certain types of pattern noise and signal processing can be detected using 2D FFTs (Fast Fourier Transforms).

I performed such an analysis of dark frames (raw) from a 5D2 and a 5D3 using ImageJ.
Here's the 5D2

and the 5D3

The ISOs from left to right are ISO 50, ISO 1600, ISO 6400, ISO 25600, and ISO 102400 (5D3).
The images have been darkened to accentuate the patterns.

Sometimes I find it helpful to view the images from several feet to see subtle features.
The "ideal" FFT would be a uniform gray.
A good guide to interpreting FFTs is here:
http://qsimaging.com/ccd_noise_interpret_ffts.html

Stong vertical or horizontal lines general indicate pattern noise in the horizontal or vertical direction respectively.
These lines are stronger for the 5D2. It has more pattern noise than the 5D3.

Little "ticks" along an axis is usually a sign of banding, often due to unbalanced channels in a multi-channel readout scheme.
This is present in both cameras to some extent.

The 5D3 ISO 102400 has the classic "spherical" look of signal processing. There is no question that this ISO is "cooked".

The 5D3 also look suspicious to my practiced eye in that the FFTs change from a horizontal line to a vertical line from ISO 50 to ISO 102400. I can barely make out a diamond shape in the ISO 6400 image. Such a transition could only come from signal processing. (Obviously subtle compared to ISO 102400!)

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Canon EOS 5D Mark II Canon EOS 5D Mark III
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