Message
Re: [colorvision_group] Re: Extended Grays reducing Print Resolution
2007-10-27 by CDTobie@aol.com
In a message dated 10/27/07 7:47:14 AM, edknight@... writes:
I've read a few gray patches (0, 25%, 50% and 75%)
Keep in mind that the profile doesn't control the tone of 0% or 100%, the paper and the black ink do...
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.
Less than 1 delta a*/ b* is very good... as long as it doesn't lean the the green direction. Even a single point of green can be unpleasant. Another thing to keep in mind is that the goal isn't necessarily simple mathematical neutrality... somehow the grays must ramp in a pleasing manner into the paper tone, as that paper tone will define white for your eye, under many viewing conditions. This can be done by biasing much of the grayramp towards paper white, or only the last section of it, where the paper tint starts effecting the eye. There are modes for both of these choices, and depending on the particular paper, and to a lesser degree your viewing light, you may find paper relative grays, or absolute grays, to be more aesthetically pleasing, and for that matter more netural appearing.
The lowest a*/b* values will not always mean the most acceptable, or the most convincingly neutral, print. Thats why tools to nudge the neutrality are almost as important as tools to produce mathematically neutral results.
C. David Tobie
Product Technology Manager
ColorVision Business Division
DataColor Inc.
CDTobie@...
www.colorvision.com
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