Re: Eye-One Pro and Profilemaker 4 Emissive Meaurement Errors
Re: Eye-One Pro and Profilemaker 4 Emissive Meaurement Errors
- Subject: Re: Eye-One Pro and Profilemaker 4 Emissive Meaurement Errors
- From: Chris Murphy <email@hidden>
- Date: Sun, 24 Nov 2002 19:43:45 -0700
On Sunday, November 24, 2002, at 04:58 PM, "John Hollenberg"
<email@hidden> writes:
As a test of the profile, I decided to measure neutral gray patches in
Photoshop
using the Spot measurement tool in Emissive mode in PM4. The results
are presented below:
Lab Value Emissive Measurement
0,0,0 2.1, -1.3, -1.4
10,0,0 6.7 -0.8, -3.8
20,0,0 14.9, -1.9,-4.9
30,0,0 24.5, -1.1, -6.7
40,0,0 34.8, -1.8, -7.8
50,0,0 45.4, -1.4, -9.9
60,0,0 55.7,-1.5,-11.8
70,0,0 65.7, -1.8, -14.1
80,0,0 75.4, -1.5, -15.7
90,0,0 85.5, -2.1, -17.1
100,0,0 95.1, -2.7, -17.6
These measured values appear to be totally erroneous to me.
The measured values are correct. The numbers from Photoshop are bogus
because they are based on RelCol rendering. Example:
Go into the color picker and create a LAB color 50,0,0 which in Adobe
RGB corresponds to 118 for R, G, and B. Make a new RGB document made up
of 118 for R, G, and B. Using the info palette set to LAB and confirm
that these RGB values equate to 50,0,0 in LAB. Now go into the Color
Settings, check the advanced mode, and change the conversion options
rendering intent to Absolute Colorimetric and click OK. Now check the
info palette measurement and it will read 50, -1, -11. The discrepency
in L* has to do with L* not being absolute. It's relative - I forget to
what, maybe it's vendor specific, but it's uncommon to get L*=100 from
a measurement device as there's always something that could have a
higher L*.
Chris Murphy
Color Remedies (tm)
Boulder, CO
www.colorremedies.com
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