Histograms
Nov 8, 2014 10:58:33 #
tenbach
Loc: SW Utah
I am trying to grasp the detailed creation of histograms..
I think this to be correct...
A sensor has x pixels cover with a Bayer array, ie each pixel has a red, green or blue filter and has a single linear luminance level associated with it and recorded as RAW data.
The camera processor creates an RGB value for each pixel using some sort of nearest neighbor algorithm producing the JPG thumbnail image on the LCD screen.
Now the questions
Is the gray histogram calculated from the luminance levels from the JPG values for each pixel??
How are the RGB histograms calculated?? Is it from the raw data of each pixel or is it calculated from the RGB values created for each pixel????
I think this to be correct...
A sensor has x pixels cover with a Bayer array, ie each pixel has a red, green or blue filter and has a single linear luminance level associated with it and recorded as RAW data.
The camera processor creates an RGB value for each pixel using some sort of nearest neighbor algorithm producing the JPG thumbnail image on the LCD screen.
Now the questions
Is the gray histogram calculated from the luminance levels from the JPG values for each pixel??
How are the RGB histograms calculated?? Is it from the raw data of each pixel or is it calculated from the RGB values created for each pixel????
Nov 8, 2014 11:05:03 #
Nov 8, 2014 11:42:54 #
tenbach wrote:
Is the gray histogram calculated from the luminance levels from the JPG values for each pixel??
How are the RGB histograms calculated?? Is it from the raw data of each pixel or is it calculated from the RGB values created for each pixel????
How are the RGB histograms calculated?? Is it from the raw data of each pixel or is it calculated from the RGB values created for each pixel????
Most lumenance histograms are calculated as you say. Some simply assume the green channel is close enough (it isn't).
The camera generated histogram is from the JPEG image produced for previewing. A RAW converter program might show an histogram based on raw sensor data, but most don't. Editors of course don't have the raw sensor data, so they can only show an RGB based histogram.
Nov 9, 2014 05:17:29 #
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