Following on from my photoshop vibrancy challenge, I thought I would talk about some photoshop techniques I’ve been playing with for changing the saturation on photographs. All thumbnails are clickable.
Original shot

Apologies to my niece Megs: I took this photo without letting her pose for it with the result that she doesn’t have some fake grin and posture in it
Technique 1: Colorize in Hue Mode

a simple but effective technique I picked up last summer:
Create a HSB adjustment layer, colorize, then use the ‘hue’ blending mode.
the greys are desaturated, and although the tone is monochrome, you retain some of the depth and range of the original.
Technique 2: Duotone in Hue Mode


The first image here is the tritone, included for reference.
Once you’ve created a duotone (or tritone in this case), you can copy it back as a layer to the original, again setting it to a Hue blending mode.
The duotone gives you an extra element of control over method 1 because it allows you to define the colour at different ranges (i.e. curves of shadows, midtones & highlights). However, you can clearly see that the resultant colours can’t be judged by those of the tritone you’re using: compare the colours here to the previous image in the set (the very tritone used to set the hues).
Technique 3: Using a Saturation-based Mask

Here’s the fun bit: thanks for my friend Marcus for the first part of the recipe.
We’ve created a channel based on the saturation of the original image and used it as a mask for a HSB desaturation of -90.
This is perhaps not the best sample image to show the effect (which loses a lot of effectiveness at small sizes), but if you look closely you can see that the center of the daisy is still a bright yellow.
‘Saturation Channel’ Recipe (Tom’s version of a Marcus original):
1. Duplicate the layer(s)
2. Hide the original layer(s)
3. add a layer of solid red, blend mode Hue
4. add a layer of solid red, blend mode Luminosity
5. Flatten visible (this should leave you with an image that goes from gray to red).
6. Use the channel mixer: I used red+150 constant-30 with the monochrome option checked to give a grayscale result
7. copy the layer and paste it into the quickmask to create a selection
8. Save the selection.
In this particular image I mucked about a bit further when using the selection as an image mask with brightness and contrast.
Technique 4: Posterizing the Saturation Mask

The Saturation-based Mask is a basis for a lot of experimentation: In this case, I posterized the mask on the HSB adjustment layer.
I think the result is remarkably subtle.
Thanks to Ian Tindale for the suggestion.
note: I originally posted all of this as a set of six pictures on flickr, but I decided it was wrong there: it cluttered up my photos, used up a valuable set (free accounts only get 3). Besides, I’d want to do a comparison like this, and it’s a discussion, not a portfolio.
So I’ve replacing the flickr stuff with a composite image and a link here.