Saturation Out and In

[Stroker]

How to extract saturation to greyscale and put it back in. Simple tricks using stock tools - all you need is Selective Colour and a Gradient Map. Lot's of possibilites, but I'm only showing the basic ideas. [details]

[Leah]

Thanks -- as you ay, this is an underdiscussed area. After playing around I can see how this is a big asset when working with a photo where some areas are already highly saturated but you want to boost saturation of the other areas, for example.

I'd be interested to see some more detailed examples of what you'd use it for, though -- sounds like you've given this area a lot more thought than most of us!

[Doug Nelson]

In another forum I saw someone asking for something along the lines of a "saturation curve", where you could actually have variable saturation in one image. I wonder if this could be a step in that direction?

[Leah]

The best results I've got have been from applying a curve to the saturation mask, so it sounds promising if I understand your other poster correctly.

[Stroker]

Doug, I did a search for 'saturation curve' and got a bunch of hits. I'll keep digging as I'm curious. If you, or anyone else, finds it before me, me mucho appreciate it.

My uses? Not much because I don't do this kind of work as much as i used to. Right now I'm mostly hobby and just work on techniques as oppossed to application. But I do have a few favorite ways of messing with Sat.

One of my favorites is to paint more or less Sat. Between SatBW and the GMap, I'll add a layer, fill it with 50% grey, and set to Linear Light. Then I'll grab the Paintbrush, set to Linear Light also, and paint in more sat or paint out sat. It's like using the Sponge tool, but with the benefit of layers.

Another thing I use it for is ChOps. If you combine a Sat mask with a Lum mask, you can create other masks for tweaks. For example, finding the areas with low Lum and high Sat. Or medium Lum and high Sat. Really cool stuff.

I was doing some link hopping and found a guy that talks about clipped colours and how to fix with a sat mask. Used a yellow flower as an example. Can't seem to find my way back to the site, though. Digital Darkroom or something. He has a way of extracting sat to grey, but I didn't check his method for this.

Another thing I've been kind of playing with is using it to mask Lum operations while leaving hues mostly alone. Just invert the sat mask and use it for a Curves or Levels or something. Will adjust the low sat lums and leave hues mostly alone. Awesome for a little extra pop, and can help greatly when converting to greyscale.

I also use this as a way to explore a photo. Before I work on a photo, I'll tear it apart. If I can see anything blatant in the smaller pieces, it will help with a plan of attack.

This is also a small part of a larger set of techniques that I use. When combined with other techniques, there is more functionality with Healing and Patch tools. Why, you can even go far beyond what Colour Match can do with absolute intent and precision.

Then the silly experiments. Like extracting sat to grey and setting to Luminosity.

If anybody comes up with a cool use, I know I would like to hear it.

At the bottom of the tutorial, I mentioned that this is different than using a single ad-layer set to Saturation. Attached is an example. On the left is a Levels ad-layer set to saturation. On the right is the exact same Levels ad-layer, but tossed inbetween SatBW and the GMap. See the difference? The only way that I can describe the difference is that extracting Sat is more 'pure'.

*The Levels adjustment is nice and tight somewhere between 40% and 60%.

edit:
Did some Googling for 'saturation curve' and found some software stuff. Near as I can tell at a glance, what I've shown is pretty much the same thing.

edit2:
Oh! I just got an idea.
I think ya'll is gonna like dis.
Hehehe.

[Cameraken]

Hi Stroker.

I’ve been playing about with this stuff quite a lot recently. I’ve been at your site for hours and all this is finally making some sense. I am actually finding some uses for splitting H and L It’s a bit like LAB in RGB.

Splitting H.
The ‘Best method’ Works fine.

Splitting S.
Great Tutorial. Thanks. The one thing the tutorial does not mention is that you have to click the Gmap to get to the Smooth option.

Splitting L
Channel Mixer Red*0.30 + Green*0.59 + Blue*0.11


I was just wondering about your idea. Did you get any further? I have not found a use for Sat yet.

Ken

[bart_hickman]

Originally Posted by Cameraken

I have not found a use for Sat yet.
Ken

Great tutorial. I have a huge use for extracting the saturation channel. So much so, that I had a script to do it in Paintshop Pro. Now I also have CS2, so I made an action to do it. This action takes the principles of this great tutorial and makes the recombination interactive through the use of adjustment layers. So you can manipulate the saturation channel and see the results in real time. When you're done, you can turn the changes on and off.

My favorite thing to do is apply a gamma-boost-like curve to the greyscale saturation channel. This does a nicer-looking job of boosting saturation than simply using the saturation adjust tool.

Here's a link to the action:
http://home.comcast.net/~zumbari/Scr...on_Channel.zip

Bart

[Cameraken]

Hi Bart.

That’s a nice idea to record an action. Unfortunately it won’t run under PS7 So it looks like I’ll have to make my own.

I have been using Strokers plug-in

http://tech-slop.serveit.org/wiki/in...=Extract_HSLum

But I have had to add the gradient manually to put Sat back.

Ken

[bart_hickman]

Sorry about that--I can't figure out how to save an older-compatible version. If I find a way, I'll probably update my link.

The version of photoshop I had before CS2 was 4.0, but I don't keep 4.0 installed because it was fairly buggy running in XP.

Bart

[Stroker]

But I have had to add the gradient manually to put Sat back.

Not necessarily true. When you use Extract HS/Lum to extract saturation, notice that there are 3 little checkboxes underneath. Leave R turned on, but turn off G and B. This will put the greyscale saturation in R and put pure black in G and B. What you end up with is something like this:

Min(RGB) = G = B = 0
Max(RGB = R = greyscale saturation

When you do that, just set the result to Saturation. To tweak, just tweak the R channel. For example, Curves > Drop-Down > Red. When you do it this way, you don't have to use a Gradient Map to put saturation back in.

Make sense?

Or you can use a G-Map. Sometimes I do and sometimes I don't depending on what I'm doing and my mood. Maybe one of these days I'll ammend a tutorial or two to include this tid-bit.

[Cameraken]

Ah! That’s much easier. Thanks for the Tip, Stroker.

Ken