Gamma, dithering and device calibration
Gamma, dithering and device calibration
- Subject: Gamma, dithering and device calibration
- From: "Mark Ward" <email@hidden>
- Date: Fri, 2 Aug 2002 10:26:53 +0100
Could you folks please help me better understand the relationship between
the gamma setting, dithering (for want of a better word) and monitor and
printer profiles?
I'm using using photoshop 6, os 9.1, and I've calibrated my monitor with the
colorvision spyder and photocal 2.5.1. I selected a gamma of 2.2 during
profile generation, and I'm using adobe1998 as my colourspace within
photoshop. (During the monitor profile generation, I had a brightness of 87
Cd/m^2, and r,g,and b all matched each other acceptably)
Should pixels of (r,g,b)=(128,128,128) now be half as bright as those of
(255,255,255)? Ie if I make a checkerboard pattern of alternate (0,0,0) and
(255,255,255) pixels and do the squinty-eyes-thing, should it look the same
as a patch of (128,128,128)? Is this where gamma 2.2 comes in - should it
make the (128,128,128) patch (a midtone?) darker than the [(0,0,0)
(255,255,255)] patch? Or should photoshop know what the gamma is, and
correct how it displays colours?
I guess what I'm asking is, with the settings I've chosen (or with any
alternative set?), should the greyscale from (r,g,b)=(0,0,0) to
(255,255,255) be linear? If not, then presumably when having printer
profiles made I'd need to specify what gamma I'm using if I want to get a
good match between monitor and print (including lighting etc.)
So far I've tried the checkerboard technique with (128,128,128) and
(255,255,255) pixels, and compared it with a patch of (192,192,192). At 100%
magnification, the checkerboard pattern was fairly close in brightness to
the solid colour patch, but a bit more blue (???).
If you could shed any light on this (doh!) or point me towards useful
resources I'd be very grateful.
Best wishes,
Mark Ward
--------------------------------------------
Dr. R.M.Ward, email@hidden
Research Fellow, IRC in Materials Processing
University of Birmingham, UK
tel (44)121 414 5236, fax (44)121 414 3441
--------------------------------------------
_______________________________________________
colorsync-users mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/colorsync-users
Do not post admin requests to the list. They will be ignored.