Photoshop
Colour and Tonal Adjustments
Colour Balance
The Colour Balance dialog is relatively straightforward to use and is effective in correcting colour imbalances. We'll work through a practice exercise to correct the waterfall image. We'll also resurrect our cat image one more time to fix up the tint problem with the tips of its fur, as promised. You'll get some insight into doing spot touch-ups with the painting tools.
The Colour Balance adjustment is one example of where understanding complementary colours will come in handy. The corrections it applies are based on them.
Colour Balance can be applied as an adjustment layer. It can also be applied to an entire layer by going to Image > Adjust > Colour Balance or using the shortcut command Ctrl-B (Cmd-B).
Practice Exercise 1: Adjusting the Waterfall Image Using Colour Balance
We described how to use colour samplers and correct the waterfall image in the previous lecture. You'll do it yourself in this practice exercise.
- Open the original waterfall.jpg image that you downloaded before you saved it as a .psd file.
- Use the Save As command and save it as colour_balance.psd.
- We're going to do a quick-and-dirty tonal correction that we know will result in a significant colour imbalance. Go to Image > Adjust > Auto Contrast.
Select the Colour Sampler tool and set the Sample Size option to 5 x 5 Average.- Pick out two areas in the waterfall that are the closest to white that you can find. As you move the tool over the image, the Info panel will display the RGB values of the underlying pixels. This may help you in deciding what points to choose. Click in the spots you've chosen to set two sample points.
We picked spots at the bottom of the right waterfall. Sampler #1 is in a very light area and is probably the best sample. Sampler #2 isn't as light but is located in an area with a lot of the same values.
The values displayed in the Info panel confirm that red is the predominant colour in the sample points because its value is higher than the green and blue components.
At the bottom of the Layers panel, click on the Add New Fill or Adjustment Layer button. Select Colour Balance from the menu.
In the Colour Balance dialog, there are three slider controls. Each slider has a pair of complementary colours at either end. To increase cyan and reduce red, for example, you'd drag the top slider towards cyan. As you drag the sliders, the values in the Colour Levels fields change dynamically.
In the Tone Balance section of the dialog, there is a Preserve Luminosity check box. When enabled, this will ensure that the tonal values won't shift while correcting the colour. Since you should always correct colour after correcting the tonal values, enabling this option is a must to retain the tonal range.
There are radio buttons for Shadows, Midtones and Highlights. These are used to apply your colour changes to those parts of the image without significantly affecting the other areas.
- Enable the Preview check box if it isn't already on. This will let you view the effect of the changes in your image while the dialog is open.
- Click on the Highlights radio button.
- We know there is too much red in the highlight (waterfall) area so try dragging the Cyan/Red slider towards cyan. You should see a noticeable improvement.
- While you're doing this, observe the Colour Sampler values in the Info panel. We dragged the slider towards cyan until both the Red and Green values were 255 in both colour samples. The blue value is lower but we'll correct that in the second step.
- Drag the Yellow/Blue slider towards blue until it also displays 255 for both samples. Don't over-correct. Stop as soon as the values match. Your waterfall should be a sparkling white now! Click OK to close the Colour Balance dialog and save your file.
- Hide and display the Colour Balance adjustment layer and marvel at the difference that it made. You can view our before and after images.
These are the settings that we used. Yours may vary slightly; it all depends on the sample points used. In comparing the before-and-after colours, you'll notice that the change affected the entire image, not just the highlights. However, the majority of the adjustment was applied to the highlights. If you were to remove or hide the adjustment layer, set a new Colour Balance layer and try to improve the waterfall area using midtones or shadows, you'd find it impossible to do.
The great thing about using this method is that you don't need a trained eye in colour. You can use the colour samplers and the Info panel as your guide. The key is in selecting what should be a neutral-coloured area in your image to base your decisions on.
Practice Exercise 2: Adjusting the Cat Image Using Colour Balance
This poor kitty looks like he's been walking through mud puddles. We're going to use a mask and a Colour Balance adjustment to clean him up.
We're going to break the rules here and forego the tonal correction step. We really don't have enough colour information to go on. We'll skip the Colour Sampler step as well since we certainly don't have a neutral area in the image to sample.
- Open your copy of Cat_extract.psd. This is the image in which we practiced using the Extract command to remove the background.
- Add a new layer and fill it with white. Drag this layer beneath the cat layer. We're only doing this so we can see the cat more clearly against a solid background.
- Click on the cat layer (Layer 0) to make it the active layer.
- Make a selection of the cat in one of two ways:
- Ctrl-click (Cmd-click) on Layer 0 to load the layer's opacity as a selection.
- Switch to the Channels panel and Ctrl-click (Cmd-click) on the alpha channel you saved previously to load it as a selection.
- Invert the selection by pressing Shift-Ctrl-I (Shift-Cmd-I) or use the menu command Select > Inverse.
- Go to Select > Feather and set the feather radius to 20 px in the Feather Selection dialog. Feathering the inverted selection will push the selection back into the area of the cat to include the outer edges. Using Feather rather than expanding the selection will ensure that the colour change will fade out at the outer border of the selection and not create a sharp transition. Because the selection border only surrounds areas of more than 50% opacity, we can't see the part of it that feathers over the cat's fur.
- Hold down the Alt (Option) key while clicking on the Add New Fill or Adjustment Layer button and selecting Colour Balance from the menu. In the New Layer dialog, enable Use Previous Layer to Create Clipping Mask and click OK. Your Layers panel should look like the one below:
The selection was automatically converted to a mask when the adjustment layer was added. The white and grey (feathered) areas of the mask (shown in the mask thumbnail) will allow the colour adjustment to affect the underlying pixels. The colour adjustment won't affect the black masked area at the centre of the cat. Masking this layer with the previous layer prevents the adjustment layer from affecting the colour of any underlying layer.
- In the Colour Balance dialog, leave the Tone Balance set to midtones. Try adjusting the slider controls to see if you can make the colour correction. You may find it helpful to zoom in on the stomach area of the cat, which is the most affected by discolouration. If you need to close the Colour Balance dialog to reposition and/or zoom in on your image, click on the OK button, not the Cancel button. Arrange your image the way you want and then double-click on the adjustment layer thumbnail to open the dialog again. Note: the Zoom and Hand tool keyboard shortcuts will work when the dialog is open.
- When you've improved the colour balance as best as you can, click OK to close the Colour Balance dialog.
- Save your file and compare your before and after images by toggling the visibility of the adjustment layer.
Here's what we ended up with using Colour Levels values of +73, -22, -64 in the Colour Balance dialog. It's not perfect but it's definitely a vast improvement.
We took it one step further and used the painting tools to fix up the stomach area, paying close attention to the area just behind the leg. First, we merged the adjustment layer with Layer 0 and locked the layer's transparency. The Eyedropper was used to sample a foreground colour from a normal area of the cat's fur. A soft, round 17 pixel Brush was set to Colour mode at 50% opacity and then the colour was applied to the greyish/purplish areas. This fixed the colour problem.
The tips of the fur still looked bedraggled from the background extraction. The layer transparency was unlocked and a small, soft Eraser brush was used to clear off some stray pixels between strands of fur. A large, soft Eraser brush was chosen and just the edges of it were pressed a few times against the tips of the fur to reduce the transparency a bit and give them a softer appearance.
So there you have it. A very difficult subject has been removed from its background and you've corrected the colour problem. The cat can be placed against any colour of background canvas and look like it belongs.
Colour Balance Summary
- The slider controls in the Colour Balance dialog are based on complementary colour pairs. Increasing one value of a pair will decrease the corresponding complementary value.
- The key to sampling colours to use for colour corrections is to pick areas that should be neutral; i.e. white, grey or black. Then you can remove the colour cast with Colour Balance.
- You can focus your colour corrections on an image's highlights, midtones or shadows.
- The Preserve Luminosity option will ensure that the image's tonal range is protected during colour corrections.
- If there is a selection in an image when an adjustment layer is added, the selection will be converted to a mask.
Colour Balance Keyboard Shortcuts:
- Image > Adjust > Colour Balance: Ctrl-B (Cmd-B)
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