From 017ee2de62e650ccbd0ec108a7a4a80c807304a3 Mon Sep 17 00:00:00 2001 From: torger Date: Thu, 14 Nov 2013 10:21:24 +0100 Subject: [PATCH] Updated docs --- rtengine/camconst.json | 49 +++++++++++++++++++++++++++++++----------- 1 file changed, 37 insertions(+), 12 deletions(-) diff --git a/rtengine/camconst.json b/rtengine/camconst.json index a8154a164..0c49386a8 100755 --- a/rtengine/camconst.json +++ b/rtengine/camconst.json @@ -261,19 +261,44 @@ so you get output on the console (you need to start RT from a console to see the output). When you load a file you will see a message of current black and white levels and if they came from dcraw or camconst.json. If you're adjusting an existing camconst.json value you can just read what it is in -the file and not need to enable verbose output. Reset exposure sliders to -neutral, and zoom in on a large clipped highlight. Move around the mouse -pointer within, it should show stable 100% on R G B. If so, the white level -is not too high, it could however be too low. To test that, go to the raw tab -and adjust the "whitepoint linear correction factor", reduce it until one of the -channels is no longer 100%, and then increase in steps of 0.01 until all are 100 -again. Usually you play around in the range 0.90 to 0.99, ie a very small -adjustment. Then divide the original white level with your adjustment to get a -new larger white level, which you then enter in your camconst.json file. The -same procedure can be used if the white level is too high, ie if you see pink +the file and not need to enable verbose output. + +Reset exposure sliders to neutral, and zoom in on a large clipped highlight. +Move around the mouse pointer within, it should show stable 100% on R G B. If +so, the white level is not too high, it could however be too low. To test that, +go to the raw tab and adjust the "whitepoint linear correction factor", reduce +it until one of the channels is no longer 100%, and then increase in steps of +0.01 until all are 100 again. Usually you play around in the range 0.90 to +0.99, ie a very small adjustment. When you've found this factor you should +apply it on the old white level to find a new larger one. As RT's "whitepoint +linear correction factor" work after blacklevel subtraction and camconst.json +want values without it we need to do some math: + +BL = black level (typically something near 0, 256, 512 or 1024, find it in the + verbose output or if available in camconst.json) +F = whitepoint linear correction factor you just found out (typically in the + range 0.90 to 0.99 if you need to increase white level, 1.01 to 1.10 if + decrease) +oldWL = old white level, found in verbose output or in camconst.json if + available. + +new white level = BL + (oldWL - BL) / F + +Note that if black level is 0 which it is for many cameras, the formula +simplifies to: new white level = oldWL / F. + +Here's an example from a Canon 1000D: black level is 256, old white level is +3651, whitepoint correction factor becomes 0.90, then new white level is +256 + (3651 - 256) / 0.9 = 4028. + +If your camera have different black levels per channel use the smallest one +as that yields the most conservative result. + +This new white level you then enter in your camconst.json file. The same +procedure can be used if the white level is too high, ie if you see pink highlights, then increase the correction factor above 1.0 until you just start -seeing stable 100% on all channels, and then divide the original white level to -get a new smaller one. +seeing stable 100% on all channels, you use the same formula to calculate the +new smaller white level. */ {"camera_constants": [