Topic: Lab Sat - ChOps like this (Page 1 of 1)

Lab is a sphere, but Photoshop insists on using a cube. This means that saturation can't exactly be rho for whatever reasons and things. So, the sphere has to be cubed. Eh? What was that? No, we won't be using a straight-edge and a compass. Rather, let's take a trip with Mr. Peabody and visit with Kai the Krause of ChOps.

Using the range -128 to 127, sat in lab as PS uses it:
Sat = Max ( abs(a), abs(b) )

(Don't ask because I don't even want to begin to explain how I know that. Maybe later if you whisper nicely in my ear.)

Since will be using ChOps in the Channels palette, the range in 0 to 255. This means offsetting by -128. We now have
Sat = Max ( abs(a-128), abs(b-128) )

You know your ChOPs, right? Just by looking at that you know the ChOps needed, right? Right? Right?

- grab some photograph and go into Lab mode
- copy it to a new layer

Now, because of the 128 thing, we will need a channel with 128 to work with in a few of the steps. Since we want the colour information and Lab seperates colour and Lightness, might as well use L* channel.

- channels palette > Lightness channel
- Edit > Fill
-- Use: 50% grey
-- Mode: Normal

Now, going to use that L @ 50% for the abs() part.

- channels > a channel
- Image > Apply Image
-- Channel: Lightness
-- Blending: Difference

Cool beans.

Now to abs() the b channel.

- channels > b channel
- Image > Apply Image
-- Channel: Lightness
-- Blending: Difference

Cool beans x2.

Now, how do we get the Max of those those two? Lighten!

- channels > a channel
- Image > Apply Image
-- Channel: b
-- Blending: Lighten

Uber cool beans.

Now all we have to do is clean it up so that it's all in one channel for easy tweaking.

- channels > b channel
- Edit > Fill
-- Use: 50% Grey
-- Mode: Normal

Uber cool beans x2.

Go back to Layers and set to Saturation. Turn it on/off and be amazed at the differences that you don't see. Oh... Ah...

To tweak, of course, you tweak the a channel. And, because of the 128 thing, you only tweak half. Yeah, kind of sucks that sat in Lab is limited to such a small range, but still a good technique for global saturation. Even if you think it sucks as a technique, it is still fun and a good exercise.

Still shaking pillars.

play.fiddle.learn

(Edited by warjournal on 03-14-2006 20:14)

It scares me that i dont understand

*sits in the corner feeling stupid*
*makes some excuse about not having enough time to do more PS*

Don't worry too much about it, Maruman. Tuck it away and maybe someday it will tickle your brain.

Shortcut ahoy.

Start with a photograph and go into Lab mode.

New Adjustment Layer > Hue/Sat

For this Hue/Sat Ad-layer:
- Colourzie turned on
- Hue = 0
- blending mode = Hue

On top of that, new layer and fill with 50% Grey.
For this grey layer:
- Advanced Blending
-- Turn off a channel

Now use your favorite method to copy merge and paste.

Tada.

It can be used also for removing unwanted color casts...

"Go back to Layers and set to Saturation. Turn it on/off and be amazed at the differences that you don't see. Oh... Ah..."

- duplicate the layer, and toggle visibility to the first one;
- leave the opacity slider at 100%;
- copy/merge;
- invert;
- set Color as blending mode;
- reduce the opacity as taste.



Retouching limited only by ones imagination[GLENN HONIBALL]

(Edited by Zenigata on 10-25-2006 23:17)

(Edited by Zenigata on 10-25-2006 23:19)

~Tucks it away~

Goes to Stupid corner w/popcorn

quote:

---

docilebob said:

~Tucks it away~

Goes to Stupid corner w/popcorn

---

Does so too, with a tin of tuna instead

And here's an interesting interview with GLENN HONIBALL.
http://bermangraphics.com/press/retouch.htm

As for being in the 'stupid corner' ... that's where I get my food delivered.

___________________________________________________________________________
The goal in Life's Journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "holy moly what a ride!"

That boy is good NoJive.
Nice link. It`s not always the technology that matters.
That was one of the most important things I learned here from Mr Garden, Weadz and DL in the early days.