Wednesday, August 29, 2012

How to Measure PTC

Albert Theuwissen explains how to measure and interpret the Photon Transfer Curve (PTC) in his latest blog post.

2 comments:

  1. What are the reasons for a deviation from a slope of 0.5 in standard deviation versus mean log-log plot? PRNU, non-linearities, others?

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  2. Hi, PRNU does not play a role, because the noise calculation takes only temporal noise into account. Non-linearity plays a role (you can see that also in the mean-variance plot), but more important is the limited dynamic range. In the mean-standard deviation plot you can observe that the curve is getting steeper and steeper if you move to larger effective output signals. So the curve has the tendency to reach a slope of 0.5 but right before coming to this point, the pixels saturate.
    Do you need more info about this effect ? I do have images and data available of devices with a larger dynamic range, and in that case getting a slope of 0.5 is no issue.

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