Datacolor User to User Support Group.

I've read a few gray patches (0, 25%, 50% and 75%) printed through
both HQ and Expert profiles with Extended Grays looking for color
shifts since my color vision isn't too good.  Will try full ramps
later.  I find that the 4 profiled print patches generally reading
closer to neutral than the HP's built-in profile for their own
advanced glossy paper(B9180 Printer) or most of my "paper whites". 
Most a* and b* readings are <1 with a very few in the 2-3 range. I
don't know the math of DeltaE, so I don't know how much drift on the
a* or b* channel is considered too much for neutral grays.

Thanks for your help and education.

Ed 



-- In colorvision_group@...m, CDTobie@... wrote:
>
> 
> In a message dated 10/26/07 8:34:05 AM, edknight@... writes:
> 
> 
> > Based on your message, I read the expert (large) target on Epson HW
> > Matte and then added Extended Grays. Using a loupe, I could still see
> > higher resolution on the 225 patch target without Extended Grays,
> > though all looked the same without magnification.  However, checking
> > with the Windows color applet, I see that the large target with grays
> > creates a profile with a slightly larger gamut (Again, not noticeable
> > to my eyes on the test file).
> > 
> 
> The 729 patch target is (mostly) about additional colors in the
saturated 
> zones, read gamut edges. The extended grays is about more
information in the near 
> grays zone. The two combined add lots of patches throughout the
color space, 
> and especially in the near gray zone. Your definition of higher
resolution is 
> not based on the accuracy of the grays in question, but rather the
number of 
> them in a given ramp. Adjusting colors (including grays) for
accuracy may 
> adversely effect smoothness. To use a check that considers ALL the
factors, you 
> would have to print each gray patch large enough to measure, and
check the 
> NEUTALITY of each, as well as how many distinct levels are present.
Adding patches 
> trades off one for the other, to some degree. Your analysis looks at
the color 
> values, not smoothness, of the added colors, and (inversely) the gray 
> smoothness, not the color values, of the grays.
> 
> C. David Tobie
> Product Technology Manager
> Digital Color Solutions
> Datacolor
> CDTobie@...
> www.spyder3.com
> 
> 
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