From 0993772520d277b0555a89bd461bf7498e465db9 Mon Sep 17 00:00:00 2001 From: torger Date: Thu, 14 Nov 2013 14:53:36 +0100 Subject: [PATCH] Yet some camconst.json doc updates: added a few comments about black levels --- rtengine/camconst.json | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/rtengine/camconst.json b/rtengine/camconst.json index 8235b8f99..295826826 100755 --- a/rtengine/camconst.json +++ b/rtengine/camconst.json @@ -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": [