In the Develop Module, the sliders Vibrance and Saturation sit right next to each other, yet have very different effects on the image, which sometimes can be subtle and sometimes drastic.
Vibrance gets applied in a curve. It affects already saturated areas the least and dull areas the most.
Saturation gets applied equally to all the colors of the image. Therefore, if you have some areas already well saturated, they will start to look unnatural.
Overall, I tend to use Vibrance more than Saturation
Saturation – Luminance: Often I go for the individual color sliders with the setting on Saturation to fine tune an image. (By clicking on the circle in the upper left corner of the field, you can select with the cursor the color in the image you want to affect. By pulling up, the saturation is increased, pulling down will decrease it.) Lately, I have begun to also look at the Luminance of a color. When Saturation is the ‘amount’ of color, then Luminance is the ‘amount of light’ in that color. The effect in an image is quite different and, when applying Luminance, you have to watch your histogram so you don’t create a hot spot. The image below is am example of applying Saturation in the highlights and Luminance in the shadows.
Split-toning: With this, you apply a selected hue to the highlights and / or the shadows. I have used this mostly with my ice crystal images to create a sense of cold. Some of them I needed to convert to greyscale in order to bring out the crystal structures. I then added ‘color’ to mostly the highlights.