Re: PDF Color Space
Re: PDF Color Space
- Subject: Re: PDF Color Space
- From: Karl Koch <email@hidden>
- Date: Mon, 14 Sep 2009 15:48:51 +0200
David,
if you really want to do it right, you´ll have to do it yourself. I
doubt that the designer understands the intricacies of profile
conversion.
The right way to do it is a DeviceLink conversion (with the proper
DeviceLink).
AdobeRGB as well as sRGB are matrix based profiles and as thus don´t
bear rendering intents other than relative colorimetric. Since
AdobeRGB is considerably larger than sRGB (especially in the greens),
a profile conversion will result in clipping – you´ll lose detail,
especially in the green area. E.g. the following AdobeRGB values will
all result in the same sRGB values:
AdobeRGB -> sRGB -> Lab
0, 255, 0 -> 0, 255, 0 -> 88, -79, 81
64, 255, 0 -> 0, 255, 0 -> 88, -79, 81
128, 255 0 -> 0, 255, 0 -> 88, -79, 81
or:
0, 255, 64 -> 0, 255, 20 -> 88, -79, 79
64, 255, 64 -> 0, 255, 20 -> 88, -79, 79
128, 255, 0 -> 0, 255, 20 -> 88, -79, 79
While a DeviceLink conversion would give you:
AdobeRGB -> sRGB -> Lab
0, 255, 0 -> 0, 255, 0 -> 88, -79, 81 (depending on the settings
in the DL)
64, 255, 0 -> 0, 230, 19 -> 80, -73, 73
128, 255 0 -> 4, 248, 0 -> 86, -77, 79
0, 255, 64 -> 0, 224, 78 -> 78, -69, 56
64, 255, 64 -> 0, 229, 72 -> 80, -71, 60
128, 255, 0 -> 0, 249, 48 -> 86, -77, 73
Clearly differentiated colors, as opposed to profile conversion.
A testfile can be downloaded from http://colormanagement.org/en/testimages.html
- Testing ToneValueDifferentiation.tif
So, if you want to retain detail in your images, you´d either have to
ask the designer to convert using an ICC-DeviceLink or do it yourself.
Best regards,
Karl Koch
Am 14.09.2009 um 13:03 schrieb Roger:
David,
Converting from AdobeRGB to sRGB on the way to creating a PDF is
nothing out
of the ordinary. It will work. There are pros and cons to this
approach but,
bottom line, it's workable. We'll assume the designer knows can to
pull this
correctly.
Roger
I am a photographer working on a catalog which, while usually printed
and mailed, is this year going to be "published" via PDF and email.
Normally I give the designer tif files which are created in RGB
Adobe 98 and then converted to CMYK using the printers settings/
profile. For web work I always use sRGB jpg files. The designer said
that the Adobe 98 tif files are fine and that when the PDF files are
created they will be converted to the proper web viewing space. Is
this correct or should I convert the tifs to sRGB? Obviously this is
not a big deal but I am curious.
Thank You in Advance
David Ramsey
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