LAB--->RGB LAB--->CMYK

LAB--->RGB LAB--->CMYK

Post by Jean Pierre Davia » Sun, 21 Apr 2002 04:36:00



Is it true that photoshop uses the lab mode as a base?

Is there LAB scanners?

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LAB--->RGB LAB--->CMYK

Post by Taci » Sun, 21 Apr 2002 05:01:16


Quote:>Is it true that photoshop uses the lab mode as a base?

Photoshop uses Lab as an intermediary when you separate an RGB file.

If you have an RGB file and use Imge->Mode->CMYK, Photoshop converts the image
internally to Lab, then separates the Lab image to CmYK.

Quote:>Is there LAB scanners?

Professional scanners? Yes. Consumer scanners? No.
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LAB--->RGB LAB--->CMYK

Post by PFig » Mon, 22 Apr 2002 08:56:47


Quote:>>Is there LAB scanners?

>Professional scanners? Yes. Consumer scanners? No.

ALL scanner, professional or otherwise, scan in RGB. They have to. Heidelberg
scanners, do convert scanner RGB to Lab for you and let you manipulate the data
with an LCH interface, but the scanners are all RGB to begin with.
 
 
 

LAB--->RGB LAB--->CMYK

Post by Chris Co » Mon, 22 Apr 2002 09:38:47




> >Is it true that photoshop uses the lab mode as a base?

> Photoshop uses Lab as an intermediary when you separate an RGB file.

> If you have an RGB file and use Imge->Mode->CMYK, Photoshop converts the image
> internally to Lab, then separates the Lab image to CmYK.

> >Is there LAB scanners?

> Professional scanners? Yes. Consumer scanners? No.

Any scanner: no.
Scanners work in RGB (until you get to multispectral scanners, still in
research).
Scanners cannot work in CMYK or LAB.
The scanner SOFTWARE has to do conversions to LAB or CMYK (yuck!).

Chris

 
 
 

LAB--->RGB LAB--->CMYK

Post by Taci » Tue, 23 Apr 2002 02:23:35


Quote:>The scanner SOFTWARE has to do conversions to LAB or CMYK (yuck!).

Or, in the case of old-fashioned analog drum scanners, the scanner's hardware.

Take, for example, an antique Hell Chromagraph CP341 I used to work with--a
three-ton, $320,000 beast of an analog scanner that is "programmed" by a large
array of dials and switches. Produces better CMYK seps than any software I have
ever seen, period. Better than ColorSmart, better than Photoshop, better than
expensive proprietary software from Scitex and Crosfield, better than any other
separation solution I've ever encoountered.

In any event, high-end scanners don't *scan* in Lab, but they certainly do
allow the user to *work* in Lab, using an ICC-based color conversion engine.

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1. HSB->HLS + RGB->Lab

I need to convert from HSB to HLS and viceversa. I wonder if I can do it
without converting HSB->RGB->HLS, and HLS->RGB->HSB.

I also need to convert from RGB (or HSB) to Lab and viceversa.

Colour space conversion is driving me crazy...

Thanks!!!
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