Re: Colorimetric Accuracy in the Field
Re: Colorimetric Accuracy in the Field
- Subject: Re: Colorimetric Accuracy in the Field
- From: Rich Wagner <email@hidden>
- Date: Wed, 05 Jun 2013 12:27:58 -0700
On Wed, 05 Jun 2013 10:04:22 -0700, Ben Goren <email@hidden> wrote:
> On Jun 5, 2013, at 9:55 AM, Andrew Rodney <email@hidden> wrote:
>
>> Bruce Fraser's Lab values from the target are based on Lab values supplied by Chris Murphy** which he states in the piece and those values differ a bit from Lindbloom.
>
> But do those values match those of the actual ColorChecker Bruce Fraser photographed?
>
> As I wrote, the quality and consistency of the ColorChecker is commendable, but it *IS* a mass-produced item and differences of a few DE aren't at all uncommon. And those differences can easily become significant with the age and condition of the ColorChecker.
>
> I'll bet you a nice dinner at a restaurant of your choice in the Phoenix metropolitan area that the N9.5 patch on Bruce Fraser's personal ColorChecker is at least a few DE from the L*=96.14 a*=0.00 b*=0.00 he assumed it was.
>
> b&
This issue is easy to deal with. If you're concerned about the accuracy of the reference measurements, you can replace the built-in ColorChecker reference measurements in the ColorChecker Passport software with spectral measurements of your own CC Passport. Just make a copy of the (Mac) app and save it as a backup, open the application package (option-click), look for the Reference folder. There's a file inside called ColorChecker24_spectral.txt. Replace it with your own spectral measurements from your Passport, close and save. You unfortunately can't do this with the DNG Profile Editor as the measurements are contained in compiled code.
--Rich
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