Photoshop
Colour and Tonal Adjustments
Other Colour Adjustment Options
There are a number of other colour adjustment options available. Some are more selective than Colour Balance (and more complex to use), some have limited effectiveness, and others are geared more towards special effects. An overview of the Desaturate, Hue/Saturation, Selective Colour, Replace Colour, Variations, Channel Mixer, and Auto Colour commands will be presented in this lecture.
Desaturate
Desaturate will remove all colour from a layer or selection, leaving a greyscale image that is still in RGB colour mode. The command is Image > Adjustments > Desaturate and it has no options.
Hue/Saturation
The Hue/Saturation function allows you to designate a target colour in an image and adjust its hue, saturation or lightness. It can be applied as an adjustment layer or to a layer by going to Image > Adjustments > Hue/Saturation.
- Edit Pop-up Menu
- If Master is selected, changes will apply to all colours in the image. The other choices are: Reds, Yellows, Greens, Cyans, Blues, Magentas. When a specific colour is chosen, changes will affect only pixels containing those colours.
- Hue
- The Hue slider will shift the colours as though moving around the colour wheel. It is tied to the two colour bars at the bottom of the dialog. The top bar shows the original placement of the colour wheel spectrum. The bottom bar shows the colour shift set with the Hue slider. Values can range from -180 to +180, each of which represents a half rotation around the colour wheel.
- Saturation
- This slider affects the strength of the hue(s). Values range from -100 (desaturated) to +100 (fully saturated).
- Lightness
- This affects the overall lightness or darkness. Values range from -100 (black) to +100 (white).
- Colourize
- This option can colourize or tint a greyscale RGB image to give it a duotone effect. The Edit menu is greyed out when Colourize is enabled so the effect is applied to all pixels. This effect was applied to the waterfall image below.
Selective Colour
Like the Hue/Saturation dialog, Selective colour also lets you targets pixels in a specific colour range for correction. The sliders are based on the CMYK colour model which makes it more difficult to use if you're not familiar with CMYK. It can be used on RGB images.
Selective Colour can be applied as an adjustment layer or to a layer by going to Image > Adjustments > Selective Colour.
- Colours
- The Colours pop-up menu choices for targeting pixels are: Reds, Yellows, Greens, Cyans, Blues, Magentas, Whites, Neutrals, Blacks.
- Method
- Determines how the colour change is applied. Relative changes the colour relative to the amount of that colour a pixel already contains. A 10% increase in the cyan value of a pixel that contains 50% cyan will increase its cyan by 5% (10% of 50%). Absolute will add or subtract the designated amount from the current colour value. A 10% increase in cyan to a 50% cyan pixel will change it to 60%.
- Sliders
- The Cyan, Magenta, Yellow and Black slider controls are used to apply colour changes to the target pixels according to the Method chosen. Values range from -100% to +100%.
Replace Colour
The Replace Colour dialog is similar to the Select Colour Range dialog in the way it functions. (In other words, it's not easily controlled.) You can select an individual colour range and change its hue, saturation, or lightness. Droppers are used to sample colours from the image and changes are applied that colour.
To open the Replace Colour dialog, go to Image > Adjustments > Replace Colour.
- Fuzziness
- This is a misnomer that refers to the selection tolerance. The higher the value, the more pixels will be included in the selection. This can be used before or after a selection has been made.
- Selection/Image
- The preview window will display a black and white mask for Selection or the colour image when Image is enabled. The Selection option is useful for confirming the extent of your selection.
- Dropper Tools
- The left dropper is used to make an initial selection from the image or from the preview window if it's set to Image. To add to the selection, use the dropper with the plus sign. To subtract from the selection, use the dropper with the minus sign.
The Sample colour well shows the average colour you've selected with the droppers. The Hue, Saturation, and Lightness sliders are used to change the colour in the areas you've selected. The Sample colour will change to reflect your settings and, if the Preview check box has been enabled, your image will also display the changes.
Variations
The Variations function will allow you to preview your image in a dialog with a number of different options applied to it in thumbnail versions. Presumably, it was designed to be usable even by those not comfortable with the other colour correction methods. It's very difficult to see the details in the small thumbnails displayed in the Variations dialog.
To open the Variations dialog, go to Image > Adjustments > Variations.
You can target highlights, midtones, shadows or saturation. To change the image, you click on thumbnails inside the dialog that look the closest to the effect you want. There is a section for changing the hue and one for tonal values. Each section shows the current version of the image as a basis for comparison. The Fine/Course settings determine how much each click will affect the image. For example, if the image needs cyan to offset too much red, clicking on the More Cyan thumbnail may apply too much cyan. Reducing the setting towards the Fine value will apply less cyan per mouse click.
Channel Mixer
The Channel Mixer is a sophisticated correction and creative tool that allows you to:
- Make colour corrections to individual channels.
- Create high quality greyscale images by choosing the strength of each colour channel's contribution.
- Work in a greyscale version of the image and apply tinting.
The Channel Mixer can be applied as an adjustment layer or to an entire layer by going to Image > Adjustments > Channel Mixer.
Once you become comfortable with colour corrections using other tools, explore the potential of the Channel Mixer.
Auto Colour
Auto Colour automatically adjusts an image's contrast and colour by looking at the values in the image itself rather than at the image's histogram.
To apply Auto Colour, go to Image > Adjustments > Auto Colour. There are no options for this command.
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| Before | After Auto Colour applied |
Other Colour Adjustment Options Summary
- The Desaturate command will remove all colour, leaving a greyscale image that is still in RGB colour mode.
- Hue/Saturation allows you to designate a target colour in an image and adjust its hue, saturation or lightness.
- Selective Colour lets you targets pixels in a specific colour range and adjust their colour using the CMYK colour model.
- In the Replace Colour command you create a selection of pixels based on their colour and can change their hue, saturation, or lightness.
- The Variations command will allow you to preview your image in a dialog with a number of different options applied to it in thumbnail versions. You click on different thumbnails to work towards a colour correction.
- The Channel Mixer is used to correct colour, create high quality greyscale images and apply special effects by manipulating the RGB colour channels.
- Auto Colour automatically adjusts an image's contrast and colour by looking at the values in the image itself rather than at the image's histogram.
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