ICC input profiles : elaboration, use, gaps
the color management is processed: a) partially with LCMS2, that made great improvements, and can now work using floating point avoiding colors cliping b) directly by computing (conversion of XYZ, Lab, RGB, gamma, etc.).rgb values are without any color space - this point is essential (the choice sRGB or AdobeRGB for example suggested by the camera is for JPG files sonly).in order to give them a more realistic look, these rgb data are modified by either a color matrix (from Adobe), or a DCP profile (from Adobe or RawTherapee), or an ICC input profile, we will below come back about these ICC profiles, their elaboration and use.the interpolation (AMaZE, AHD, DCB.) takes place after by rgb data modifying (the image can be visually evaluated on a screen): the interpolation shouldn't modify the colorimetry (or a very few) and that is the case for all the existing interpolations in RawTherapee (deltaE94 due to interpolation is approximatively 1, so negligible), in the other hand, at the limits (upper highlights.the default white balance is the one chosen by the user on his/her camera for the shooting!.Le first step that is essentially carried out on a Dcraw basis (thanks to D.Coffin) consists in reading all types of raw files, with their proprietary coding: data depth, 12 or 14 bits, sensor saturation, white balance.Initial raw processing before RGB conversion Read the raw file and use its data Of course, this document is far to be exhaustive, the subject is complex.You can change this behaviour going into "Preferences" and checking "Use working profile for main histogram and navigator" The histogram display as well as the browser can be configured: by default, the displayed values take into account the "Output profile".The reader shall preferably have minimal knowledges about color management : matrix triplet, RGB, XYZ, Lab, color space, primaries and colorimetric profile.RawTherapee automatically detects the system profile, however you can enter the screen icc filename in « Preference/ Color Management / Monitor Profile ».
the DTP94 probe I own, and for which it doesn't exist any more drivers for Windows) give very good results the processing time is quite long (about an hour). Under Windows, MacOS or Linux, a software like DispalGUI from Argyll, combined with a probe of quality, even old (e.g.The created profile is for the monitor only and must never, in any case, be used either as input profile or output profile. However, it is recommended to calibrate the screens with one of the many products in the market: colorimetric probe plud software.This document doesn't aim to deal with the whole colorimetry aspects that aren't specific to RawTherapee, like for instance:.More over it does not take into account possible malfunctioning (bugs) still unsolved ! Note: This document only deals with RawTherapee 4 and computing with real numbers, and not RawTherapee 3. To explain the use of some functions that may look obscure to newcomers. To explain the main steps principles in order to allow the user to be able to weight what is at stake.ģ. To summarize the raw file processing pipeline from a colorimetry point of view and to highlight key points and gapsĢ. This document aims at several objectives about colorimetry:ġ. 1.5 What happens when we are in a "Working Profile" or when we change of "Working Profile" or the settings?.1.4 Work in the color space chosen by the user (working space "Working Profile").1.3 rgb => RGB conversion - Working space "Working Profile".1.2.3.9 Illuminants Diagrams and Color Rendering Index (CRI).1.2.3.6 "Blackbody" illuminant and "A: tungsten".1.2.3.4 Colored object – illuminant – observer.