Re: maclife.de
Re: maclife.de
- Subject: Re: maclife.de
- From: Karsten Krüger <email@hidden>
- Date: Wed, 3 Sep 2008 15:04:10 +0200
Am 03.09.2008 um 14:06 schrieb Bob Frost:
First, ICC camera profiles used by raw converters today are designed
to process output-referred (i.e., rendered) image data, not scene-
referred (i.e., raw) image data. Furthermore, the sequence and
placement of color transformations described in an ICC camera
profile can prevent other image processing stages (such as highlight
recovery algorithms) from performing optimally. Third, there is no
standard that describes the input color space of the ICC camera
profile color transformation (it is often, but not always, a tone-
mapped set of RGB camera coordinates). Consequently, ICC camera
profiles are not portable: they can only be used with the raw
converter for which they were explicitly created in the first place.
Using an ICC camera profile designed for one raw converter with
another raw converter nearly always produces incorrect (though
sometimes entertaining) results.
Which still is no reason why we are **not allowed** to generate and
use selfmade ICC-profiles.
In contrast, DNG camera profiles are designed specifically to
process scene-referred image data. The color matrices, color tables,
and tone curve transformations are applied in separate stages
(instead of all in one step) to minimize exposure dependencies and
to enable other image processing stages to perform optimally. The
entire color processing model is described in the DNG 1.2
specification and SDK, thus enabling portability of DNG camera
profiles among all raw converters that support DNG 1.2. Unlike ICC
profiles, DNG profiles can store color adjustments separately for
two illuminants (usually illuminants A and D65), which are used by
the raw converter to derive the final color transformation
automatically from an image's white balance. Finally, multiple DNG
camera profiles can be embedded within DNG raw files, thereby making
DNG images self-contained and ensuring that the photographer's
chosen "color appearance" stays with the file wherever it goes. "
This is only partly true - it still depends on the RAW converter and
it's output. The portability can not be guarantied. And when there are
multiple DNG camera profiles, which one is to be used ?
In my eyes the DNG-profiles are more or less macros on how the Adobe
RAW converter should behave - which is fine for a lot of situations,
but very subjective to set up.
ICC profiles are only about color - and only color. They do less, but
might do it better, are created in a more scientific way and more
reproduce-able.
There is one other issue that bothers me - Adobe forces me to render
an image to sRGB, AdobeRGB or WideGamut-RGB. Perhaps I need to comply
to international standards and need to render to eciRGB v.2, or need
an ISOcoated v2 CMYK file. Why is it impossible for Adobe to let me
chose my own destination color space ?
Thanks,
Karsten
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden