Message
Re: [colorvision_group] Re: Using Colorimeter to evaluate and edit profiles??
2008-05-12 by CDTobie@aol.com
In a message dated 5/11/08 9:04:04 PM, rschoner@... writes:
My problem seems to be that I have difficulty translating the LAB
values to adjustments for the RGB sliders.
There aren't really 'RGB' sliders, only color sliders (which, admittedly are not labeled as 'positive a star' or the like
This gets compounded by
changes in one color affect the other colors.
Thats the way life works...
For example I profiled
Epson Glossy paper with Image Specialists Ink. The original reading
for the gray patch was LAB 49.45, 4.10, -0.06 or RGB of 115.6.
105.8, 108.28. SInce this had a pinkish cast I started reducing the
cyan/red slider. After several iterations and a complete re-start I
wound up with slider adjustments of Cyan/Red +2, Magenta/Green +2,
Yellow/Blue -4. This gave measured values of LAB 47.93, 0.26, -0.07
and RGB 104.7, 104.2 104.4 essentially neutral and confirmed by
different prints; colors seem to be very close, if not right on. At
this point I am happy.
It may not be possible, but maybe the Spyder software could have LAB
correction sliders as well as the conventional RGB sliders.
Unfortunately people would take them too literally, and expect units of the exact size of Lab value units. We can't know exactly how much change, in Lab units, an adjustment will make, as that will vary with factors beyond our control. You are the first to ask for this, what I hear more often is a request to make our units line up exactly with Photoshop values... again not really practical for similar reasons. So the recommendation is: if you want to use Photoshop RGB units, or see your adjustments visually on screen, build a Photoshop RGB curve set and once that is doing what you want, import it into Spyder3Print and apply to your profile.
You never mention what printer you are using, but its unusual with a 'two grays' printer to have results after profiling that are as far off neutral as 4 a* units. Is this by any chance a one gray, or no grays, printer?
C. David Tobie
WW Product Technology Manager
Digital Imaging & Home Theater
Datacolor
CDTobie@...
www.datacolor.com/Spyder3
**************
Wondering what's for Dinner Tonight? Get new twists on family favorites at AOL Food.
(http://food.aol.com/dinner-tonight?NCID=aolfod00030000000001)