[argyllcms] Re: Determining proper error value for -r

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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