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

On 2006 May 26, at 2:09 PM, Gerhard Fuernkranz wrote:

> Ben Goren wrote:
>
>> 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.
>
> Ben, I'm  objecting the statement  "a low -r value  will produce
> more  accurate colors". That's  basically  not  the case. A  low
> smoothness factor will  indeed result in a model  which fits the
> _training set_ with a low error.

Well, that's why I used ``may''  instead of ``will,'' and ``not so
low as to have real trouble with noise.

What I'm  driving at is  that, within the  range of values  for -r
which are  at least large enough  to be an accurate  reflection of
the error bands of the data,  the lowest value should, I think, if
I'm understanding it right, produce the most accurate colors. It's
also the value  most likely to bump into  non-linear properties of
the  printer. At the  other extreme,  a value  that's ridiculously
high  will produce  results more  akin to  not even  profiling the
printer in the first place.

Cheers,

b&

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