Histogram mode in X3F Tools

Started Mar 16, 2013 | Discussions thread
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Roland Karlsson
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Histogram mode in X3F Tools
Mar 16, 2013


I have added a histogram mode in my X3F tools. You might get something like this if you import the output to Excel.

This s the XR, XG and XB channels from this image

Which I got from MrBlissfly

There are some things you can see.

  1. The X red layer has less than half the exposure.
  2. Both the X green layer and the X blue layer have a strange behaviour when the values starting to get large. There seems to some posterization. But, it might not matter. The photon noise at e.g. 900 is 30, and the posterization is only 16 and above 2000 or so. I assume this posterization is due to Sigma simplifying the A/D conversion. I assume XR will behave similarly if it can be exposed for clipping at 4095.
  3. The strong peak in the XG and XB channels is the bright white chimney in the middle of the image. Its very near to 4095, which I assume is the clipping level for the A/D converter. The XR channel does not show this peak. So, I assume that some of the red buildings is quite near maximum, which seems to be at approx, 1700. I wonder if XR also clips at 4095? In that case, this white chimney is one stop below clipping for XR.
  4. NOTE that the y scale is logarithmic.
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