Untagged RGB to Lab conversion
Untagged RGB to Lab conversion
- Subject: Untagged RGB to Lab conversion
- From: David Remington <email@hidden>
- Date: Mon, 17 Dec 2001 21:35:40 -0500
This topic has been beat around here a few times but I still have
questions. I'm going to try re-phrasing it a few different ways to
see what the group can come up with. I'm currently evaluating
PhaseOne and Better Light scanning back cameras for an upcoming
purchase. As a part of this process I would like to compare capture
values of various targets (Macbeth regular and DC, Kodak Q-60...etc)
to target definition file measured values. Measured values are ICC
Lab. Captured values are RGB. How can these values be meaningfully
compared? For that matter, and this is a question no doubt best
directed to PhaseOne and Better Light, how are RAW RGB values
determined? Sensor R,G, and B filters as primaries plus secret sauce?
Is there any way to convert from RGB to Lab without defining the RGB
colorspace? Having said this I should add that I'm fully capable of
seeing the circular logic involved. If you could make an ideal
conversion to Lab from your raw camera data you would have no need of
a camera profile. What I would like to investigate is just where that
raw data is starting from. Is it starting anywhere? Is RGB data
completely defined by the box you draw around it?
--
David Remington
Photographer
Digital Imaging and Photography Group
DN-90
Widener Library
Cambridge, MA 02138
617-787-4032