+Chromatic Adaptation - What is it...what does it do?
“Chromatic Adaptation” is most widely described as a dynamic mechanism of the human visual system to compensate for white point changes when viewing an object in different illuminations. If a white object is viewed in different lighting (i.e., “bluer” daylight and incandescent lighting), the object retains its white appearance as long as the viewer is “adapted” to the lighting.
It is important to note that a chromatic adaptation transform (CAT) is used in imaging systems to map image appearance between different illumination sources. Some of the most popular CATs are selectable in i1Profiler: “Bradford (BFD CAT)”, “Sharp CAT”, “CMCCAT2000”, and “CIECAT02”.
The ICC (International Color Consortium) specifications are for D50 (or 5000K) illumination for color measurement as well as lighting for judging printed samples. The ICC spec for Profile Connection Space (PCS) is also for D50. Because ALL profiles connect to PCS, all non-D50 profiles will use the selected CAT to convert to D50. The CAT will use mathematical models to transform non-D50 data to the ICC specification of D50.
The selected chromatic adaptation transform will be used only when non-D50 settings are used (i.e., display white point other than D50). Each CAT will use a slightly different formula. The default in i1Profiler is “Bradford” and it is the most widely used. Adobe uses the “Bradford” CAT in all of their applications. Most other CATs are partly based on the Bradford CAT.
Additional information on CATs:
- Bradford (BFD CAT) is the default CAT in MonacoProfiler andi1Profiler
- CMCCAT2000 is a modified version of BFD CAT
- CIECAT02 is a modified version of CMCCAT2000, default CAT of ProfileMaker 5
- Sharp (Sharp CAT) trys to overcome some problems of the BFD CAT but is still in development