[Digikam-users] Re : Re : Re : Choose another ICC profile for converting pictures

Paulux nvlplx at yahoo.fr
Fri Oct 7 16:29:31 UTC 2011


The conversion to an output color profile is always made in an calibrated workflow when you print : DK makes it itself, that's why you can specify an output color profile for your printer in DK's settings.
For printing labs, some (the more professionnals, perfect for unique jobs but not for mass ones) make properly the conversion from sRGB to the needed profile (in this case, I don't have any problem), some don't make anything if you refuse automatic corrections and ask you to convert your pictures in their ICC profiles. 

And yes, sometimes (especially for prints on aluminium or PVC) I would need to separate pictures in CYMK, then in a corresponding profile.  


________________________________
De : Martin (KDE) <kde at fahrendorf.de>
À : digikam-users at kde.org
Envoyé le : Vendredi 7 Octobre 2011 16h59
Objet : Re: [Digikam-users] Re : Re : Choose another ICC profile for converting pictures

Am Freitag, 7. Oktober 2011 schrieb Paulux:
> Thanks to all for answers.
> 
> @Martin (KDE) : thanks, I know what is soft proofing and how to use
> it in DK ;) (even if the result is not satisfying, too red), and
> it's absolutely not what I want to do.
> 
> @Remco (french ?) : English is not my native language, so perhaps
> I've not clearly explained my thought : I know the differences
> between color spaces and ICC profiles, but the only tool to
> convert a picture in this domain is the color space conversion
> tool. And that's exactly what I whant to do (because I kown what
> I'm doing, thx).  Commercial printing services often (always) make
> automatic corrections on the pictures you send them. Although,
> some of them offer the ability to refuse this way and purpose ICC
> profiles for each combination of printer, paper and ink they use.
> So if you want to use their services, you MUST convert you picture
> in  the ICC profile corresponding to the product you want.

Huch, that is new to me. My printing lab provides profiles and does 
not require me to convert the pictures to any specific colour space. 
An labs using automatic corrections are not worth the try for serious 
photo printing. the results are unpredictable.

I still don't see the need for converting a photo to a output colour 
profile (besides the lab requires it - but why?).

The only reason I can imagine of is if the printing colour space is 
much smaller than the working colour space. Then you have the control 
in how the colours should be corrected. But this can be done in the 
working colour space (or a different working colour space) as well. 
That's what the soft proofing for.

Do you have to separate the photo to CYMK as well?

Martin

> 
> The quickly way to do it with DK should that color space conversion
> tool allows to choose some output ICC profiles. How to do it ? 
> 
> PLX
> 
> 
> ________________________________
> De : Remco Viëtor <remco.vietor at wanadoo.fr>
> À : digiKam - Home Manage your photographs as a professional with
> the power of open source <digikam-users at kde.org> Envoyé le :
> Vendredi 7 Octobre 2011 8h20
> Objet : Re: [Digikam-users] Re : Choose another ICC profile for
> converting pictures
> 
> On Friday 07 October 2011 07:31:05 Martin wrote:
> > Am 06.10.2011 21:12, schrieb Paulux:
> > > I've a precision to make : as I understand the Digikam way to
> > > manage ICC profile, it now (I'm sure it wasn't the case in the
> > > past) sorts profiles by type (i.e. the output profiles menu
> > > only shows and manages output type profiles, and so on).
> > > That's roughly a good idea for the digikam control panel, BUT
> > > not for the color space conversion tool in picture editor and
> > > batch tool. This one only shows display ICC profiles, but it
> > > should offer output ICC profiles in order to completely
> > > control the colors behavior before print works, especially
> > > with remote laboratories.
> > 
> > I don't think it is a good idea to convert a photo to the colour
> > space of the printing machine. These profiles should be used for
> > soft proofing only and this has nothing to do with the workspace
> > colour profile (these must not and mostly do not match the
> > display profile).
> 
> ..
> Even worse: screen and printer profiles are NOT colour spaces, but
> only output corrections from a (device-independent) colour space
> to an imperfect output device. They are specific for a combination
> of a colour space and a device.
> 
> A colour space describes how a colour we can see under standardised
> lighting conditions is encoded in an RGB triplet. This is
> absolutely device- independent.
> 
> So a colour workspace cannot 'match' a display profile, they are
> completely different beasts and should be used together to get the
> best output possible.
> 
> Yes, I know both colour spaces and device profiles have .icc or
> .icm extensions, but again, they are completely different
> concepts.
> 
> So, please leave your images in the sRGB colour space, unless you
> REALLY know what you are doing:
> a lot of questions concerning dark, muddy, unsaturated colours in
> prints come from people using e.g. Adobe RGB as editing colour
> space, and then sending of those images to a commercial printer
> (99+ % of those expect sRGB and don't check...)
> 
> Remco
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> Digikam-users mailing list
> Digikam-users at kde.org
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