[argyllcms] Re: Camera Profiling using ArgyllCMS
- From: "Pascal de Bruijn" <pmjdebruijn@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 29 Nov 2008 17:46:20 +0100
On Fri, Nov 28, 2008 at 6:17 AM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:
> Pascal de Bruijn wrote:
>>
>> I thought I noticed that as well. But aren't there any conventions
>> about this? My
>> guess is most software is written towards use with Adobe's CMM...
>
> The ICC spec. makes a recommendation that CLUT be used before
> matrix, but who knows what actually happens with some software.
> A CMM or application writer doesn't have to think much about Adobe's CMM,
> they just have to make profiles work with their software. As the creator
> of profiling software, I haven't thought too much about Adobe's CMM
> either - if I'm creating profiles that comply with the ICC spec.,
> they are likely to work with Adobe's CMM.
>
> [ I've seen a profile with both matrix and CLUT entries that is
> marked as Lab PCS - talk about confusing! ]
>
>> Using -a x and -r 2.5 seems to improve the profile quite a bit.
>> Excessively high
>> values like -r 5 don't seem to make much of an impact either way.
>
> The matrix shaper is the poorest fit to the data, which is not unusual given
> the small number of model parameters. When there are few test patches,
> or the data is very noisy, a matrix profile may give the best result. It's
> certainly best in terms of smoothness.
I tried this, using a single shaper+matrix, and the results are
baffling. The results
look reasonably accurate.
I've tried single gamma+matrix as well, but that sortof misses some
contrast. I'm
guessing gamma is always a clean curve, while a shaper allows more complex
forms?
>>> I know that the author of UFRAW believes that using a single curve for
>>> all
>>> >> three channels is the correct approach and it appears that authors of
>>> >> ProfileMaker agree him. At some point I will add a switch to LProf to
>>> >> allow
>>> >> users to
>
>>> >> I know that the author of UFRAW believes that using a single curve for
>>> >> all
>>> >> three channels is the correct approach and it appears that authors of
>
>> Well, I'd love for ArgyllCMS to be able to do this as well, optionally.
>
> Why ? What do you think this will do ?
Nevermind, Argyll can do this, but not with a LUT. The single shaper+matrix
option only generates a single curve.
>> The photos I'm using to subjectively "verify" the profile quality are
>> taken in unobscured sunlight as well.
>
> It's still unclear what the problem is, since you haven't described it or
> given any examples of it.
I'm sorry about this, but the most prominent examples I have I prefer to not
publish. I could look for other examples... But sofar I'm quite satisfied with
the single shaper+matrix profiles.
Thanks for the suggestions and help!
Regards,
Pascal de Bruijn
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