CMS problems

All about SilverFast HDR and HiRepp (48bit HDR processing)

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Gregory C
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CMS problems

Postby Gregory C » Wed May 26, 2004 7:43 pm

on my iBook, I have the following CMS settings when working with jpeg images from my Canon camera:

Color Management:
Input > internal: Use embedded profile
Internal > monitor: ColorSync
Internal > output: RGB

Profiles:
Input: none
Internal: AdobeRGB1998
Gray: Generic
Output: none
Rendering: perceptual

Embedded profiles:
Embedded profile: Camera RGB Profile
Embed ICC profile: On
Profile to embed: AdobeRGB1998

I want to embed the AbodeRGB profile in the image so that I have the best possible range when printing. the problem is that the images all appear slightly darker and redder when I embed this profile. if I embed my iBook's calibrated monitor profile, the images appear to be more 'natural'. the histograms are also very different when I switch the Internal profile.

images saved to disk have the 'natural' looking preview icon but still retain the darker/redder look when opened in the Preview application which supports ColorSync. I therefore can only guess that the preview icon does not contain any profile information.

I'm using SF_App on OS X 10.3.3.

a long time ago, Lasersoft support suggested that I use my monitor's profile as the Internal profile but that wouldn't that limit the colours when printing? Another significant person has also told me that I should be using the Adobe profile for the Internal profile.

so what settings should I be using? is there a problem with CMS when using SF App?

I have to upload my images to an online service which charges for every photo change. you can therefore imagine that I want to make sure that my settings are optimal and correct before I hand over the images and my money to the online service.


one other question. does anyone have recommendations/opinions regarding images destined for use on the internet? can/should we rely on ICC profiles for guaranteed appearance? does Windows use the profiles? I'm on a Mac where profiles are used by the web browser.


regards
Gregory

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LSI_Noack
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Postby LSI_Noack » Fri Jun 04, 2004 3:07 pm

Dear Gregory

I'd like to answer your posting on behalf of Kristian Kratzenstein, who's account is available right now.

Regards, Sonny

...........................................................................................................

Dear Gregory,

The problem could be the Adobe RGB. In most time, if you are using standard JPG images, they are created with sRGB. this is used as embedded profile. The conversation from sRGB to Adobe RGB could have slightly differences.
In this case you should use sRGB as internal colorspace.

Why : sRGB is a much smaller colorspace than AdobeRGB, so this colorspace seem to be not a good choice. But an conversation sRGB -> sRGB has less problems, and if the picture is allready available as sRGB, an conversation to AdobeRGB doesn't give you allready cut colors back.
If you have switched your camera to another profile (I could do so on my 300D), you should use that profile.

On PC CMS is not used by default. Or lets say, sRGB is set as default. All devices are handled as sRGB devices, if they have no profile, or CMS is not used. Thats the reason, why JPG's are also sRGB by default. CMS on PC (ICM2.0 from Win98) is bad documented and not easy to use for developers (you should know a lot to use).

kind regards
Kristian Kratzenstein


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