Shangara
lists-at-shangarasingh.com (Shangara Singh)::6/11/04::12:12 pm:: GMT-0000

>For those who do not own C1, the workaround is to export the file in
>ProPhoto RGB and then convert it in Photoshop to your preferred working
>color space.

This is not really what I'd call a workaround if Adobe RGB was causing
problems in the first place.

why?

there is potentially a massive hit on image data - when in taking
(converting) that data from a large working space (PPRGB) to a smaller
(ARGB). As I understand it, the choice of ProPhoto RGB in the original
file processing step would be done to avoid clipping the detail in
areas of saturated colour in the processed file? right. 

The move that you suggest: 
>then convert it in Photoshop to your preferred working color space.
will damage the file in the same way, it's easy to test.

Take a saturated RAW image, 
1:
<process to> Pro photo RGB [you might even up the saturation a bit to
assist the experiment, just as far as that of a real bright image],
now, look at the Photoshop Levels histogram, it should ideally not be
clipped.

2: 
process the same image to ARGB.

3:
Now, duplicate the proPhoto image and convert one copy to to ARGB.

[Try Perceptual and RelCol (just to prove it to yourself that the RI
choice between Perceptual and RelCol is irrelevant at this stage].

Now look at the histograms, if the image was saturated there will be
very little diference between the clipped result [3] you now have - to
what you'd have received [2] by processing to ARGB in the first place.

SO, the moral of the story is that, since Perceptual Rendering is not
available when converting TO a workingspace, whether from an input
space or from another workingspace, there is agreat opportunity to dame
file at this stage in the proceedings.

As I wrote to Chris:
<To me this is an extremely important issue, since, everywhere, every
day, digi users are clipping scans and camera files in one fell swoop
as they convert images to their chosen [sometimes unsuitable]
workingspace.>

Finding a good way to avoid this entirely is what I'd call a
workaround, it's something I worked on for about 4 years.


Best Regards

Neil Barstow
Consulting in Imaging & Colour Management
http://www.colourmanagement.net/
http://www.apple.com/uk/creative/neilbarstow/

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