Selective Colour adjustment appears to be unique to Photoshop. You may be able to achieve similar effects with other image editing programs, but the Photoshop tool is very easy to locate and use – and produces excellent results. This tool is designed to let you vary the amount of process colours in the primary colours in a digital image – without affecting other colours in the picture.
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Selective Colour adjustment appears to be unique to Photoshop. You may be able to achieve similar effects with other image editing programs, but the Photoshop tool is very easy to locate and use – and produces excellent results. This tool is designed to let you vary the amount of process colours in the primary colours in a digital image – without affecting other colours in the picture. In this feature we’ll look at simple changes for suppressing or emphasising selected colours. One of the most useful applications of Selective Color correction is for subduing the over-saturated blue skies that result from inappropriate use of polarising filters, as shown in the illustration below.  A typical shot in which use of a polarising filter has created a dark and excessively saturated blue sky. Start by opening the image you wish to work on and click on the Channels palette, checking you can see the four composite channels (RGB, Red, Green and Blue). Selective Colour adjustment is only available when you’re viewing the composite channel.  On the top toolbar, click on Layer > New Adjustment Layer > Selective Colour. Then click OK in the New Layer dialog box.  Now move to the Adjustments palette. This provides the controls for making all adjustments. The default setting is shown in the illustration on this page.  A drop-down box at the top of the palette lets you select which colour you wish to adjust. Sliders below it increase or decrease the components in the selected colour. Below the sliders are two buttons: Relative and Absolute. When the Relative button is checked, moving each slider changes the existing amount of cyan, magenta, yellow or black by its percentage of the total. For example, when you’re working on an area with pixels that are 50% yellow and add 10%, the percentage of yellow increases by 5% (10% of 50% = 5%) to 55%. Check the Relative button when you want to retain areas of pure white in pictures; because pure white contains no colour components, it’s immune to colour adjustments in this mode). Checking the Absolute button lets you adjust colours in absolute values. In this case, adding 10% to pixels that are 50% yellow increases the percentage of yellow to 60%. Absolute colour adjustment works on the basis of how close a colour is to one of the options in the Colours menu. Since 50% yellow is midway between white and pure yellow, it will receive a proportionate mix of adjustments defined for the two colours. Because the white areas in the image we’re working on are relatively small, we’ll opt for the Absolute mode for this demonstration. We’ll also work on the Blue colour channel, which should be selected in the Channels palette and also the Adjustments palette.  Dragging the Black slider to the right increases the percentage of blue in the image, making the blue sky darker and more saturated. Dragging it to the left decreases the percentage of blue in the image, making colour in the sky appear more natural-looking. The illustrations on this page show the changes possible with the Black slider.  Dragging the Black slider to the right makes the blue sky darker and more saturated.  Dragging the Black slider to the left decreases the percentage of blue in the image, making colour the sky appear more natural looking.  The adjusted image. Note that other colours in the image remain unchanged and there is no need to select a specific area for adjustment, which makes this a quick and easy method of correcting specific colour casts. Dramatic colour changes can result from adjusting the Selective Colour sliders. Our sample image shows a deep red flag iris with a distracting out-of-focus yellow flower behind it. Moving different sliders can change the colour balance in the image to emphasise or subdue different hues.  Because the Adjustments palette works on the process colours (CMYK), you have to think complementary colours when deciding which colours to change. The best way to see how each slider changes colours is to select Neutrals in the Colours drop-down menu. The illustrations below show the effects of moving each slider right and left.   Colour changes produced with the Cyan slider.   Colour changes produced with the Magenta slider.   Colour changes produced with the Yellow slider. Selective Colour adjustment can also be used to achieve more subtle changes in individual hues. Using the same original image and Selective Colour adjustments, we’ve boosted the red in the flower and subdued the yellow blotches in the background with the following settings:
 The adjusted image resulting from the Selective Colour adjustments shown in the table. So far, we’ve only shown how this tool acts on the entire image; if you want to use it on a selected area, use one of the selection tools to create a new layer containing that area (Layer via Copy) and apply the adjustments to this layer only. In the example shown, we’ve deepened the colour of the sea and increased its saturation by using the sliders for the Cyan colour band on the selected area shown in Layer 1.  The original image with a pale, washed-out sea. 
Selective colour adjustment on Layer 1, which contains the area of sea, produces richer, deeper colours in this area.
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