Adjusting Contrast


The contrast of a photo is the difference between the darkest and lightest areas of a photo. With too much contrast, you end up with overly dark and bright areas; with too little contrast, your photo appears flat.

To adjust the contrast of a photo:

  • In the Adjust panel, drag the Contrast slider to the left to decrease the contrast or the right to increase the contrast.

What the Contrast slider does

In Figure 4.39, the photo of eggs in a nest was quite flat, with little difference between the light and dark areas of the scene. In Figure 4.40, I've increased the contrast significantly to give the photo more depth and vibrancy. Note that most photos are unlikely to need significant contrast adjustments; usually a little nudge will be all you need.

Figure 4.39. This photo is too flat, with too little difference between the dark and light areas of the nest.


Figure 4.40. By increasing the contrast, I made the individual twigs in the nest stand out, giving the picture more depth and detail.


Note how the mountain ranges in the histogram have been flattened and spread out by the increase in contrast. If I had reduced contrast, the mountain ranges would have been squished in and up instead. Put another way, increasing contrast distributes the pixels in the photo over a greater range of brightness values, whereas reducing the contrast increases the number of pixels within a small range.

Tip

  • Like the Brightness slider, though to a lesser extent, the Contrast slider is an unsophisticated tool. You're better off using the black and white point sliders in the Levels histogram to set which colors should be considered pure black and pure white, which has essentially the same effect as using the Contrast slider. For details, see "Adjusting Black and White Points," later in this chapter.


What Else Would I Do?

Since this photo has a lot of detail in it, I'd definitely increase the sharpness to define the edges of the twigs further, and I'd probably warm up the temperature a bit (see "Adjusting Temperature," later in this chapter). Lastly, I'd decrease the exposure just slightly to darken it up a touch.





iPhoto 6 for Mac OS X. Visual QuickStart Guide
iPhoto 6 for Mac OS X
ISBN: 0321423313
EAN: 2147483647
Year: 2004
Pages: 225
Authors: Adam Engst

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