Re: Theoretical CMYK Profile "and Lch"
Re: Theoretical CMYK Profile "and Lch"
- Subject: Re: Theoretical CMYK Profile "and Lch"
- From: Roger Breton <email@hidden>
- Date: Sun, 14 May 2006 07:34:27 -0400
> I use the "hue, saturation, and brightness" sliders instead. What's the
> big difference.
>
> Glad to learn,
> Daniel
Big difference is that HSB is related to RGB, it is not device-independent.
Lch is calculated from Lab, it *is* device-independent.
Lch makes color editing a breeze because it is intuitive. Quick: tell me
what color is a* -40 and b* - 35? You can't. I can't. Unless we happen to
know this color by heart. But if I tell you c = 40 and h = 250 then we can
readily tell it is some kind of saturated blue. Sometimes, I'll prefer
working with Lab numbers but most of the time I prefer Lch. It is difficult
to tell the difference between two Lab colors but with Lch it is a cinch.
(IMO, a* and b* are made for masochist) Another example: what are typical
caucasian skintone colors? Quick? Ah! Between 45 and 55you say? Yes. And
how easy was that! In comparison, you'd expect an Asian skin to have a
higher yellow component, so the hue angle would have to be higher, maybe
around 70 (I haven't study this extensilvely, I'm just making the numbers
up for argument sake but you see the logic). Lch *is* much easier than Lab.
More examples still. Typical grass color? Typical sky color? Typical
stawberry color? In HSB "AdobeRGB", the answer would be one set of numbers
but in sRGB or ColorMatch or ProPhoto it would be another set of numbers:
how many different sets of numbers do you want to memorize for all the
colors you work with? Tell me. To me and all the color people I know and
most of my clients, Lch is user-friendly. Much more so than Lab. XYZ? Well,
we can make up what the Y stands for in an absolute sense but, further than
that, it's hard to put a perceptual meaning on X and Z. RGB, yes, real easy,
Photoshop is built on this metaphor. Lab is great in itself as it frees us
from the servitudes (hope that's the right word) of monitors, printers and
scanners. True, Lab allows us to tie in with color management systems and
color measuring instruments. But Lch is the cherry on the icing. I'd rather
talk "hue angle" with my clients than with cryptic a* and b* numbers. Yes,
occasionnally I talk HSB with my students, to introduce them to thinking
perceptually about color. It's there so why not use it. But I quickly bring
them back into colorimetry, Lab and Lch. I remember the first time I ever
saw Lch. It was at a Heidelberg show. Man, did that seem alien to me then.
But today, it is flowing into by veins like blood. Ah! I breathe the fresh
air of Lch. How soothing. Believe me, there is nothing out of this works
about Lch once you understand it. It becomes no more difficult than filling
up at the gas station. But once you're into it, you won't want to go back to
HSB -- ever.
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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