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Yet some camconst.json doc updates: added a few comments about black levels

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torger
2013-11-14 14:53:36 +01:00
parent ac7905eeb3
commit 0993772520
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rtengine/camconst.json
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@@ -300,6 +300,26 @@ highlights, then increase the correction factor above 1.0 until you just start
seeing stable 100% on all channels, you use the same formula to calculate the
new smaller white level.
About black levels:
-------------------
Unlike for white levels it's much more common that black levels can be
derived from the format. Either it's simply 0 (typical for Nikon cameras), or
it can be derived from masked pixels (typical for Canon cameras) or otherwise
be extracted from some tag. Some formats are have built-in subtraction
information and are pre-processed by DCRaw to end up at a black level of zero
(Phase One's IIQ). In all, you typically should not care about the black
level in camconst.json: any information that can be derived from the raw file
itself should not be specified in camconst.json! Sony's ARW2 is one of the
few exceptions (which has a single black level around 512), but DCraw
generally has good constants for these already.
Currently we have chosen not to provide any guide how to measure black levels
as we don't think it will be a common task (it's also more difficult to do
than measure white levels). If you experience a black level issue it's more
likely due to a format parsing bug which should be fixed in DCRaw and/or
RawTherapee's raw format parser.
*/
{"camera_constants": [