[argyllcms] Re: Determining proper error value for -r
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Thu, 25 May 2006 19:09:58 -0700
On 2006 May 25, at 5:30 AM, Graeme Gill wrote:
> As I indicated, I'd be surprised if you could see much visible
> difference varying -r from 0.5 to 2.0 (V0.53). Any difference it
> makes is likely to be a couple of delta E somewhere, at the
> most. For proofing, it might be worth playing with, but not for
> a whole lot else.
Sounds like just using -r 2.0 for my parents will probably solve
any problems I'm having from that, and that I can assume that any
remaining problems have more to do with ID10T errors than -r.
> It's all a trade-off. A higher -r value gives a smoother
> profile. It also gives greater error between the test points and
> the profile. Is that error noise ? - some of it. Some of it is
> the smoothed shape of the interpolation not matching the actual
> shape of the underlying device response. That's probably an area
> of research that is worth going into.
I'm starting to suspect that it may be the same kind of tradeoff
as represented by perceptual v colorimetric rendering intents. A
low -r value (but, of course, not so low as to have real trouble
with noise) may produce more accurate colors at the expense of
smoothness in photographic images. A high -r value will result in
colors that're less accurate, but perhaps not so inaccurate as to
be noticeable outside of a side-to-side comparison. I'm pretty
sure from some preliminary testing, though, that too high an -r
value will start to cost you fine detail, so it may remain
something that needs to be tweaked individually.
>> Would that be time and resources that us non-C-hackers could
>> help with? If it means, for example, some grunt work of
>> creating and measuring charts or hacking together Perl programs
>> or spreadsheets to analyze them, I'd be more than happy to
>> volunteer. And I won't complain if it turns out that it's a
>> dead end. Well, not very loudly, at least.
>
> Perhaps. The real issue is in figuring out an approach to
> extract real information from all the randomness implicit in
> real world measurements.
Well, if you need anything, give a holler. Considering the smokin'
deal I got on Argyll in the first place, I figure it's only fair
to pay some sort of a kickback....
Cheers,
b&
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