Re: Theoretical CMYK Profile "and Lch"
Re: Theoretical CMYK Profile "and Lch"
- Subject: Re: Theoretical CMYK Profile "and Lch"
- From: "Daniel Lowicki" <email@hidden>
- Date: Sun, 14 May 2006 20:00:57 +0200
**how come pressing reply never includes the list?**
Roger,
I know about the advantage of editing in a perceptual way. People tend ask for
"a little bit lighter", "a little bit too saturated", and "not quite the right color".
This is the advantage I see in having these parameters for editing.
IMO I still don't see a difference between:
shortening a chroma vector or reducing saturation,
turning the hue angle in Lab or HSB/HSV color space,
or adding L* or brightness to a color.
Again just IMO .. not many will be able to specifiy a typical color for xxx in LCh.
LCh edits, in my understanding, are mostly relative to the current "look" (as I said .. a little
bit more or less of saturation or brightness or another hue angle).
Just my 5 cents.
br
Daniel
Roger Breton wrote:
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 =
250s 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 45s and 55syou 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 70s (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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