Wayne Larmon wrote:
>
> Henry Richardson wrote:
>
> > I have a general question: How do you know if your profile is
> > correct?
>
> Good question. When you wrote to Colorvision, did they send you
> PDI_Target.jpg? This is a test picture and you are supposed to
> look at it on your calibrated system and see if it looks like it
> has a color cast. I've got PDI_Target.jpg, but it doesn't seem to
> be too exacting a test. Your monitor's color balance can vary a
> lot before you'd notice a color cast.
>
> I'd like to know the same thing: How do you know if your profile
> is correct?
>
> Wayne Larmon

Don't know about the others but I use Norman Koren's charts as a first level sanity check. You go to

http://www.normankoren.com/makingfineprints1A.html

scroll down to the "Gamma and black level chart" to make sure you're black level is Ok and your gamma is what you think it is. Then you go to

http://www.normankoren.com/makingfineprints1B.html#gamma_3lvl

to make sure your gamma stays the same at different luminance level. Then you scroll down to the three color charts to make sure your gamma is consistent across all colors.

As for the PDI target, I think there is a ColorChecker image in it. I vaguely recall measuring that portion of the image and thinking how constant the patches are. The thing must have been computer generated and and pasted to the base photo. If you have a ColorChecker, you can display the PDI target and compare the ColorCheck image in there against the real thing. Just be careful ot display the PDI target properly--I think the file is untagged but it's actually in Adobe RGB colorspace, not the usual sRBG.

As for profiling a laptop screen and not getting expected results, it might have been the laptop itself. I'm typing this on an old IBM T20. Its screen was profiled with an Eye-One Pro spectrophotometer but it fails all the sanity checks above. The same setup on my photo editing system passes all the tests with flying color and then some. The laptop screen just couldn't control the tones finely enough to show the adjustments. And worse, in an attempt to bring down the color temperature of the T20 screen, iMatch has seriously compressed the blue channel. Now blue transitions on the latop screen are banded and grainy. Your mileage will vary of course...

Andy