>Am 31.12.2012 01:14, schrieb Eckhart Pedersen: >> On 2012-12-31 00:03, Jose Carlos Garcia Sogo wrote: >>> One post on behalf of Pascal de Bruijn >> Very much appreciated, thank you! >>> Hi, >>> >>> Time to get some confusion out of the way. >>> >>> A typical complete camera input profile consist of two things: curves >>> and an XYZ matrix. >>> >>> The default color processing of Darktable (and most other open source >>> raw converters) use the Adobe DNG D65 XYZ color matrix (camera >>> specific), but that means the curve is missing. Which we complement by >>> applying a mostly brand specific basecurve. >> Does this mean that if I were to create my own input profile based on a >> test chart and with the correct settings, I would be able to get (more >> or less) natural looking images without a base curve?
Yes, because a proper (ICC) camera input profile has an XYZ matrix and curves internally. So it's basically the same thing, just applied in a single step. So you need to disable the basecurve because otherwise you'd have two sets of curves being applied on top of each other. As written earlier, Darktable uses the Adobe DNG D65 XYZ matrices (via dcraw). These do not come with curves. Other raw converters supplement this (visible or not) with an arbitrarily deformed 2.2 gamma curve. We just took it a step further to provide vendor tuned curves out of the box which are user visible and controllable. We are very transparent in that way. So to get a so-called neutral color rendition, anything but a custom color profile is mostly just an arbitrary choice. Now here are some notes on how to do a custom profile for darktable: For lightsource use whatever you commonly shoot with, natural daylight like unobscured sunlight work fairly well as a generic light source. Get a Wolf Faust IT8 chart, shoot (RAW+JPG) so the chart is complete in the image, but as large as possible, so it'll likely cover 90% of the image area. You might need to shoot the target at a slight angle because of potential glare. Do a spread of shots from underexposed to overexposed, you'll likely need a slightly overexposed image Open up the JPEGs, and search for a JPEG where the GS0 patch measures between 90-95 in a 0-100 scale, so using GIMP to measure the V in HSV should be good enough. Load the corresponding RAW into Darktable, disable the basecurve and sharpening. In the 'input color profile' and 'output color profile' plugins set everything (except the display profile) to absolute colorimetric and linear-rgb Next use crop, to compensate for the vertical keystoning, and crop the target so only the target is left (so it will cover 100% of the image). Next use spot white balance, on GS1 to GS15 or so. Export to 16bit TIFF, (absolute colorimetric/linear-rgb). scanin -v -G 1 -p -dipn output.tiff /usr/share/color/argyll/ref/it8.cht R080505.txt exiv2 output.tiff (replace MAKE/MODEL below accordingly) colprof -v -A "MAKE" -M "MODEL" -D "samsung nx100" -C "Copyright (c) 2012 Pascal de Bruijn. Some rights reserved." -a G -q m output (for more accuracy you might want to try -a S (which will likely give you more realistic blacks, though the curve may be less smooth) cp output.icc ~/.config/darktable/color/in/samsung_nx100.icc So use this new profile, disable the basecurve (or set it to linear), and select the "samsung nx100" profile in the "input color profile" plugin. In the very long run, I might do a blog post about this, but don't hold your breath. Regards, Pascal de Bruijn ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only -- learn more at: http://p.sf.net/sfu/learnmore_122412 _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
