Primary Image Adjustments
Photoshop offers several image adjustments, but only a few are used most often. Commands such as Levels and Curves are used by professionals to achieve outstanding results. These professional imaging techniques may take a little time to get comfortable with, but the power they offer is worth your investment.
The Levels command corrects tonal ranges and color balance issues. With this command you can fix poor exposure. Additionally, you can perform color correction by manually identifying a white point and black point in the image. Nearly every image can benefit from making a Levels adjustment.
To understand Levels, it is essential to be able to read a histogram. This graph works as a visual guide for adjusting the image. The Levels adjustment has its own histogram that is visible when working in the Adjustments panel. You may also want to call up the Histogram panel (Window > Histogram) and leave it open while color correcting. You can also expand the Histogram panel by clicking the submenu and choosing All Channels View. Let’s give the command a try:
- Close any open files, and then open the file Ch10_Levels.tif from the Chapter 10 folder on the DVD.
- Add a Levels adjustment layer by clicking the Levels icon in the Adjustments panel. Levels is also available from the Adjustments menu (Image > Adjustments), but the adjustment layer is more flexible for future modifications. Be sure to select the Preview check box so changes update onscreen.
- This photo was shot under mixed light, but you can reset the black and white points of the image to fix the exposure. In the Adjustments panel, move the white Input Levels slider to the left. This affects the image’s white point and allows you to reassign where white should begin in the image.
- Move the black Input Levels slider slowly to the right. The more you move the black slider to the right, the more contrast is introduced into the image.
- The true power lies in the middle (gray) Input Levels slider. By moving this slider, you can modify the gamma setting. Effectively, you can use the middle Input Levels slider to change the intensity of the midtones. This adjustment can be made without making dramatic changes to the highlights and shadows, and lets you better expose an image. Move the slider to the left to add light; move the slider to the right to subtract light.
- In the future if you need to edit the adjustment, simply select the adjustment layer in the Layers panel and manipulate the controls in the Adjustments panel.
When working with the Levels adjustment layer, you may have noticed the Auto button. This command button triggers an analysis of the histogram data by Photoshop that is then used to modify the individual controls of the Levels adjustment. In many cases this results in an image that is properly adjusted for color balance and exposure issues. In others it will get you closer to a corrected image.
- Close any open files, and then Open the file Ch10_Auto_Levels.tif from the Chapter 10 folder on the DVD.
- Add a Levels adjustment layer by clicking the Levels icon in the Adjustments panel.
- Click the Auto button to perform an automated adjustment for the image. The image’s levels and color are adjusted.
- To refine how the automatic adjustment works, hold down the Option (Alt) key and click the Auto button again. A new dialog box opens.
- Select Find Dark & Light Colors and Snap Neutral Midtones to create a very natural balance of colors for the image.
- Click OK to close the dialog box.
In the first Levels example you made a Levels adjustment to all the channels evenly. In the Auto-Levels example, you let Photoshop adjust the levels and remove color cast using an automated algorithm. The Levels command can be further isolated to a specific channel by clicking the drop-down list in the center of the Levels dialog box. This allows you to tackle color cast issues, such as spill from a background, a bad white balance, or a photo shot under mixed or colored lighting.
- Close any open files, and then open the file Ch10_Levels_Color_Balance.tif from the Chapter 10 folder. Notice how the image has a greenish tint.
- Add a Levels adjustment layer using the Adjustments panel. You will use the Levels command to fix color and exposure issues.
- Select the Set White Point (white eyedropper) in the Levels dialog box. Click an area that should be pure white. For this image, click a bright area in the white pillar. If you click an area that is not bright enough, the whites in the image will overexpose. (You can click the Reset button—it looks like a circular arrow—at the bottom of the Adjustments panel to reset the Levels command, if needed.) After you click, you’ll see that some of the color spill has been removed.
- Select the Set Black Point (black eyedropper) in the Levels dialog box. Click an area that should be pure black. Choose an area such as a jacket or a dark shadow. This will adjust the color balance and the exposure.
- The image’s color balance should now be better. Adjust the middle Input Levels slider to brighten the image.
You can also use the Levels command to correct skin tones and isolated areas in an image. The Set White Point and Set Black Point eyedroppers work well, but sometimes it can be difficult to find a pure white or black point in your image. Let’s try fixing color and exposure manually:
- Close any open files, and then open the file Ch10_Levels_Isolated.tif from the Chapter 10 folder.
- You need to fix part of the image that has dramatically different lighting than the rest of the image. Look at the bottom-left corner: The indoor lighting is throwing off the rest of the image.
- Use the Polygonal Lasso tool to select the door region. After making the selection, choose Select > Feather and enter a value of 5 pixels to soften the selection. Making a selection first causes the adjustment layer to attach a mask to isolate the color correction to the selected area.
- Add a Levels adjustment layer. You will make a Levels adjustment on each channel to fix color and exposure issues.
- From the Channels menu in the Adjustments panel, choose red or press Option+3 (Alt+3) to select the first channel. Notice how the histogram is skewed to the left. Move the white Input Levels slider to the outside edge of the histogram where it begins to rise. Move the middle (gray) Input Levels slider to balance the histogram data evenly on both sides.
- Switch to the green channel by pressing Option+4 (Alt+4). Move the black and white Input Levels sliders to the outside edges of the histogram. Adjust the middle (gray) Input Levels slider to balance the histogram.
- Make the same adjustment to the blue channel by pressing Option+5 (Alt+5). The image should now appear color balanced. If needed, you can return to the individual channels to tweak color balance.
- Switch back to the composite view by pressing Option+2 (Alt+2). You can now make a standard Levels adjustment to tweak contrast and exposure until you are satisfied.
Most users will either use Curves a lot or they won’t use it at all. The Curves interface is more complex than Levels, which scares away many users. While Levels gives you three control points (highlights, midtones, and shadows), the Curves adjustment allows for up to 16 control points. This can significantly open up more options when adjusting color and exposure.
Let’s try the Curves command on a practice image:
- Close any open files, and then open the file Ch10_Curves_Practice.tif from the Chapter 10 folder.
- Add a Curves adjustment layer by clicking the Curves button in the Adjustments panel. When you first open the Curves interface, there are two points (one for white and one for black).
- Add a single control point in the middle of the line (click at an Input Value of 50%).
- Pull this new control point down to lighten the image (toward the lighter area on the Y axis). You can pull the point up to darken the image. Notice that the Input and Output values update as you drag.
- The adjustment is applied gradually throughout the entire image. Multiple points can be employed for contrast adjustments based on tonal range.
The primary advantage of Curves is that you have precise control over which points get mapped (whereas in Levels you do not). Another benefit is that Curves adjustments can use several points connected by a curved line (as opposed to Levels, which uses only three control points) to make adjustments. So, color correction can be applied in a more gradual manner (without the hard clipping that can be associated with Levels).
- Close any open files, and then open the image Ch10_Curves.tif from the Chapter 10 folder.
- Add a Curves adjustment layer by clicking the Curves icon in the Adjustments panel. The curve has only two points on it—one representing the black point; the other, the white point.
- It’s now time to add more control points to refine the curve. To do this, you’ll use a Curves preset. Click the menu to select a Curves preset in the Adjustments panel. Choose the Strong Contrast (RGB) preset. Notice that the image now has more contrast in the shadows and highlights, and more visual “pop.”
- Experiment by adjusting the five control points. Try to further emphasize the shadows in the image. Continue to experiment by moving the control points (you can use the up and down arrow keys for precise control).
The Hue/Saturation command lets you adjust the hue, saturation, and lightness of color components in an image. Additionally, you can simultaneously adjust all the colors in an image. This command can work in two ways:
- To adjust colors in an image that appears slightly out of phase or skewed toward a color, such as an image that appears to have a blue overcast
- To create stylistic changes by dramatically changing colors in an object, such as trying out different combinations of colors in a logo
When combined with a selection command (such as Color Range), the Hue/Saturation command can be used to selectively enhance colors in an image.
Let’s give the command a try:
- Close any open files, and then open the file Ch10_Hue_Saturation.tif from the Chapter 10 folder. You’ll subtly tweak the color in the motorcycle.
- Choose Select > Color Range and click the motorcycle body to make an initial selection. Hold down the Shift key to add to the selection. Adjust the Fuzziness slider to soften the selection. Use the Localized Color Clusters to further constrain the selection. Click OK when you have a suitable selection.
- Click the Hue/Saturation button in the Adjustments panel to add an adjustment layer.
- The two color bars at the bottom of the dialog box represent the colors in the color wheel. The upper bar shows the initial color; the lower bar shows the new color. Drag the Hue slider to the left until maroon appears under red.
- Additionally, you can adjust Saturation (which is the intensity of the color) and adjust Lightness (which adds white or black to the image). Increase Saturation to +15 and decrease Lightness to -20.
A Hue/Saturation adjustment can be a very quick way to experiment with color options. You can use it to quickly change the fill colors of an object by making a global adjustment. This works well when experimenting with different color combinations. Let’s try it out:
- Close any open files, and then open the file Ch10_Logo_ Adjustments.psd from the Chapter 10 folder.
- Select the layer thumbnail of the Hue/Saturation adjustment layer to access its controls in the Adjustments panel.
- Adjust the Hue slider to try out different color combinations.
Tinting a photo
You can also use the Hue/Saturation command to tint an image. If you are working with a grayscale image, you need to convert it to an RGB image first.
- Close any open files, and then open the file Ch10_Tint.tif from the Chapter 10 folder.
- Add a Hue/Saturation adjustment layer.
- Click the Colorize box to tint the image.
- Adjust the Hue slider to try out different color combinations. Adjust Saturation and Lightness to refine the tint.
The adjustment layer automatically has a Layer Mask attached, which allows you to mask the effect.
- Click the Layer Mask icon for the Hue/Saturation adjustment layer.
- Select your Brush tool and press D to load the default colors of black and white.
- With a small black brush, paint the flowers so the original red shows through. If you make a mistake, you can press X to toggle back to white for touch-up.
When working with photos, many choose to have very saturated and rich colors. The problem with too much saturation is that it can cause clipping (a flattening of the range of colors). To help with this, Photoshop offers the Vibrance command. Unlike Saturation, Vibrance only boosts those parts of a photo that are less saturated. It also respects skin tones, which means photos look more natural when pumping up the intensity of color.
- From the Chapter 10 folder, open the image Ch10_Vibrance.tif.
- You’ll first add a Saturation adjustment layer for comparison. In the Adjustments panel, click Saturation icon to add a new adjustment layer.
- Drag the Saturation slider to the right until the colors in the image start to clip.
- Discard the Saturation adjustment layer by clicking the trash icon at the bottom of the Adjustments panel. Click Yes in the dialog box that appears.
- In the Adjustments panel, click the Vibrance icon to add a new adjustment layer.
- Drag the Vibrance slider to the right to increase saturation without color clipping.
- To add a little more saturation overall (in a gentler fashion than the Saturation adjustment layer), use the Saturation slider in the Vibrance adjustment layer.