Re: Tool for camparing an image of a target and the targets tdf
Re: Tool for camparing an image of a target and the targets tdf
- Subject: Re: Tool for camparing an image of a target and the targets tdf
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Tue, 27 Nov 2001 12:09:15 -0600
Peter Siegel wrote (in reference to measuring the delta E between a picture
of a target and its reference file):
>
We are doing this as a test, we are interested in the color performance of
>
an array capture devices (digital cameras, scanners etc.)
Since the picture of the target is (probably) RGB and the reference file
values are CIEXYZ or CIELAB, you cannot compare the two without first
translating the RGB values into a CIE equivalent. This translation involves
a profile. A report of delta E usually measures the profile's ability to
translate the *average* RGB value for a patch (averaged over an area of the
patch) into the proper Lab value from the reference file. This may be a
poor metric of color performance of a capture device, since it ignores
things like dynamic range, number of significant image bits, noise,
sharpness, edge anomalies, demosaic artifacts, etc.
I have made digital camera profiles with zero delta E from both $100 and
$20,000 digital cameras. It says nothing about the relative color quality
of the two devices.
Good luck with your tests, but be careful!
--
Bruce J. Lindbloom
www.brucelindbloom.com