In the Develop module, basic color corrections generally are best made in the following order:
- Apply tonal corrections to set the correct white point and maximize the tonal range in the image, using the histogram and the Basic panel.
- Adjust the overall brightness and contrast, using the Brightness control and the Tone Curve panel.
- Apply sharpening and noise reduction, using the Detail panel.
- Add special effects such as decorative lens vignetting or specific color adjustments, using the HSL/Color/Grayscale, Split Toning, and Vignettes panels.
The following exercise takes you through the first two steps of this typical image-correction process.
Adjusting White Balance and Tonal Range
For this exercise, you'll start by adjusting white balance for a photo, using the histogram and the controls in the Basic panel. Then you'll improve the tonal range by lightening the image—especially in the shadow areas.
- In the Filmstrip, select the photo you want to adjust. For this example, we're using a photo of a church in portrait orientation (see Figure 1).
- As this photo is in portrait format, hide the top panel (press F5) and the Filmstrip (press F6) to make more space in the Loupe view for the vertical orientation. Press T to hide the toolbar. In the right panel group, expand the Histogram panel and the Basic panel.
- In the Basic panel, the White Balance is currently set to As Shot. The Temp control shows that the shot was taken at color temperature of 4800 K (kelvin), which appears to be just about correct. However, we want the color of the stonework to look slightly warmer. Select Daylight from the WB (White Balance) menu in the Basic panel. The Temp control now shows a color temperature value of 5500 K, and the image looks a little too warm. Use the Temp slider to reduce the temperature to about 5250 K.
The image is slightly too dark overall. You can see this fact reflected in the histogram, which shows the distribution of luminance (brightness) in the image. The darker the pixel, the further left it's recorded in the histogram; a lighter pixel is mapped further to the right. A peak in the histogram represents a large number of pixels of a similar brightness in the image. The tonal range for this image looks a little weighted toward the left (see Figure 2).
When you adjust an image's tonal balance, you can use the histogram as a reference as you work to achieve a more even distribution of tone over the full range from dark to light. If you make an image too dark, part of the distribution curve moves out of range to the left of the histogram. This is known as clipping and represents a loss of color information from the image. For the pixels in the truncated portion of the curve, differences in brightness have been lost and every pixel is mapped to black; the shadows have been clipped. If you lighten the image too much, the curve is truncated at the right end of the histogram and the highlights are clipped.
Once the histogram is spread over as much of the range as is possible without clipping highlights or shadows, you can redistribute the curve to produce a well-balanced image.
- The small triangles in the upper corners of the histogram are clipping indicators. If the curve is clipped at either end of the histogram, the indicator turns white. There's already some truncation of the left end of the curve for this image, and a white triangle indicates that the shadows are being clipped. To see which areas of the image are affected, move the pointer over the clipping indicator. Clipped shadows are shown as bright blue in the image; clipped highlights are red. Some color detail is being lost in the railings and planters in the foreground of our church image. Click the clipping indicator to highlight the clipped shadows permanently. Press J on your keyboard to turn on both clipping indicators, or right-click (Mac: Control-click) in the histogram and choose Show Clipping from the context menu (see Figure 3).
- The Auto Tone command usually serves as a good starting point for adjusting the tonal range. Watch the histogram as you click the Auto button in the Tone section of the Basic panel (see Figure 4). The histogram shifts slightly to the right and the image becomes lighter overall. You can see at a glance that the left end of the curve is not as truncated; there's much less clipping of the shadows.
- Move the pointer slowly across the histogram from left to right. The range of brightness values in the histogram is divided into four distinct zones, which are highlighted in turn as the pointer moves over them. At the same time, the name of each area is displayed in the lower-left corner of the Histogram panel: Blacks, Fill Light, Exposure, and Recovery (see Figure 5). These names are shared by four of the controls in the Basic panel.
To change the tonal balance within any of these areas, you can drag the relevant portion of the curve directly in the histogram. Drag to the right to brighten that portion of the tonal range, or drag to the left to darken it. Alternatively, you could use the Exposure, Recovery, Fill Light, and Blacks sliders in the Basic panel.
- Darken the bright church wall and lighten the shadow area in the lower left of the image, using the Exposure and Fill Light sliders. To darken the brightest part of the church wall, drag the Exposure slider to about -0.38. To lighten the shadowed areas to the left of the building and in the foreground, drag the Fill Light slider to about 25. This change also takes care of the clipped shadows.
- Press the Backslash (\) key repeatedly to toggle between the edited and unedited versions of the image in the Loupe view. In this way, you can quickly evaluate your current improvements against the original image.
The image is now much better lit but appears somewhat flat. Increasing the clarity can add depth to an image by heightening local contrast, the differences in brightness between small adjacent areas of the image. The eye is very sensitive to changes in local contrast. On a larger scale, contrast describes the difference between significant bright and dark areas in the image. You'll adjust the contrast globally using the Tone Curve panel later in this lesson.
- The Clarity setting is best adjusted at a magnification level of 100% or greater. Zoom the photo to 100% by clicking the 1:1 zoom ratio in the Navigator panel. Reposition the image so that you can focus on the colonnades and the lightest part of the curved stone wall. Set the Clarity to about +50 (see Figure 6).
- Undo and redo the last step a few times to compare the image quickly with and without the increased clarity setting. Drag the image in the Loupe view to review the effect in a different area. When you're done, click the image to return the zoom level to Fit.