[argyllcms] Re: Argyll and 30-bit colors
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 16 Aug 2016 08:14:14 -0700
On Aug 15, 2016, at 8:13 PM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:
Overall I'm a bit unconvinced by it all.
Calibration is already > 8 bpc, and profiling
doesn't sample in enough detail for > 8 bpc to
be of much significance (i.e. what does it
matter that you are restricted to 16 million colors out
of 1 Billon, if you are only measuring a few
thousand of them ?).
I don't think these points can be overemphasized -- and you've just hinted at
the scope of the problem.
With a few notable exceptions, the limits of human perceptive resolution stop
at around 1 DE. That's much closer to 7 bits than to 8. Basically every display
has more than 1 DE variance from corner to corner, even ignoring the viewing
angle changes of LCDs. And they all drift with time, some more than 1 DE. And
even the measuring instruments themselves don't have perfect inter-measurement
repeatability. Add it all together, and you discover you're using Ray's Rule of
1) Measure with a micrometer.
2) Mark with chalk.
3) Cut with an axe.
In terms of dispcal
This, of course, brings in all of the relevant notable exceptions --
linearization, side-by-side comparison of samples on the neutral axis, and
Guys, Graeme's right -- not that that's surprising. Most consumer-oriented
display profiling solutions sample all of 2 bpc (64 colors) in their default
settings, and few let you do more than 3 bpc (512 colors). Few Argyll users are
profiling their displays at 4 bpc (4096). Even I, insane as I am, don't go
beyond 4.5 bpc (12K). (I let it run overnight, so why should I care how long it
Of course, the sample generation algorithms aren't aligning themselves to the
low-bit whole-number values; they're drawing from larger palettes in a way
that, hopefully, does an intelligent job of oversampling problem areas and
undersampling well-behaved regions. But, even still, Ye Olde 6 bpc "thousands"
color mode of days of yore has all the resolution anybody needs for profiling
and then some.
Calibration, again, is another matter entirely -- and I must admit being a bit
excited to hear that Graeme is thinking of ways of improving that. Argyll
already does a superlative job...but can I be excused for eagerly anticipating
something even better?
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