Re: GaMapICC v0.5
Re: GaMapICC v0.5
- Subject: Re: GaMapICC v0.5
- From: Marco Ugolini <email@hidden>
- Date: Mon, 25 Jan 2010 13:30:42 -0800
- Thread-topic: GaMapICC v0.5
In a message dated 1/25/10 11:02 AM, Klaus Karcher wrote:
> I appreciate your honesty.
>
> I agree with you: the rel. col. Photoshop conversion looks better than
> the GaMapICC conversion (at least on screen).
>
> The tonality shift in the GaMapICC version /might/ be intentional and
> appropriate depending on your source viewing conditions (I tried md-pp,
> mt-pp and pp-pp but was not able to reproduce your results exactly. Did
> you apply any changes to the image after conversion? e.g. downscaling or
> sharpening?)
>
> Please note also that Photoshop automatic black point compensation for
> device->display transformations might affect the screen assessment
> (Photoshop doesn't simulate the "true" black point unless you activate
> "Proof Colors" and select the "Simulate Black Ink" checkbox in the
> "Proof Setup" window).
Klaus,
True as that is, all images viewed on screen undergo that compensation --
the GaMap image as well as any other one. Therefore, the viewing conditions
should make the results comparable.
>> Please let me know if other GaMap conversion settings would produce better
>> results.
>
> Please give me some time to find out what's going wrong before I go into
> detail.
>
> And just one additional note in order to guard against
> misunderstandings: Image specific gamut mapping is no silver bullet. It
> does not magically provide the optimal result straightaway in each and
> every case. There are many cases where much simpler methods like black
> point compensation and clipping are just the right thing. GaMapICC with
> 100% filtering should do nothing else but apply exactly as much gamut
> compression as necessary to avoid clipping. It can not decide how much
> clipping might be good for an image.
>
> In addition GaMapICCs gamut filtering option should provide a
> continuously variable control to adjust the gamut mapping between "no
> clipping" and "no gamut compression", but obviously this does not work
> as expected yet.
My little exercise is meant to test under which conditions "image-specific"
gamut mapping may be preferable to the regular kind we have in Photoshop.
With this one image, it doesn't seem to produce superior results. But it may
with other kinds of subject matter and tonal/color structure, or with a
different set of conversion parameters (since there is a fairly large number
of combinations available).
Please share positive examples you may have encountered.
> Many thanks for your feedback again,
> Klaus
You're welcome. Exchanges of data and techniques are what a forum like this
is for.
And thank you for sharing so generously the fruits of your work.
Marco Ugolini
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