DeltaE madness
DeltaE madness
- Subject: DeltaE madness
- From: MSP Graphics <email@hidden>
- Date: Mon, 15 Oct 2007 13:32:16 -0700
I'm no delta E worshipper but I sometimes cringe at blanket dE
numbers such as "< 2 dE not distinguishable". I can tell you for a
fact that .75-1.0 dE on a midtone gray patch is certainly visible
while 2-3 dE on primaries/secondaries is difficult to see. In other
words, it depends.
That's right, and I've never made such a statement. Yet we have
people here making judgments/claims based on something like .3
average DeltaE(76) between the RIPs! It's ludicrous. Further, it's
one thing comparing patches and another comparing actual images,
where the erroneous color may or may not be conspicuous or even
present. Why don't we talk a bit more about which sorts of errors
are the MOST frequent source of trouble, like gray balance?
As far as all RIPs getting decent dE numbers and an excellent visual
match, 'tis true, but the distinguishing feature among the higher-end
RIPs is the ability to MAINTAIN that level of accuracy. There's only
a couple of RIPs that I consider to have the right technology to
maintain those kind of dE numbers over time (needing to re-profile
the entire system doesn't count in my book).
Let's clarify the waters a bit. The drift in the system is always the
printer, ink, and paper, not the RIP per se. However well or poorly
the color holds up over time is purely a printing function. So then
it's a question of how easily and well the RIP allows one to correct
for that. Assuming no huge system change (like swapping in a
different brand of ink or paper) the RIP can realign the color either
by a simple relinearization of each color ramp or, better, reading a
large sampling of solid, tints, and overprints. You're right, not all
RIPs do the latter, and it is really superior, especially if it's
iterative. And to be clear, the proofing RIP I sell does this, and my
statements about accuracy should be placed in that context. But let's
be honest, this process takes a bit of time--the price we pay for
accuracy. The sort of "free lunch" option is one of these RIPs with
an HP Z-Series printer, and either auto-schedule the process for down
time or manually start it before lunch or shift's end.
Good discussion!
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