What every iPhoto user should know about image editing

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The Adjust tab

Apple places the Adjust tab at the end of your edit options because many iPhoto users prefer the easier adjustment options found in the Quick Fixes and Effects tabs that precede it. Were they to see the Adjust pane first thing after revealing the Edit area, they might be scared off and immediately click away with a “Holy smokes! That’s too complicated for me!”

I assure you that it’s not. Let’s take a peek, section by section.

Histogram: The hills-and-valleys graph you see at the top of the Adjust pane is called a histogram. This graph represents the distribution of tones—from dark on the left to light on the right—contained within your image. The higher the peaks, the more pixels are present within that tonal range. So, if you see a lot of peaks at the far left side of your image and few on the right side, your image is going to be dark. Peaks at the far right indicate that areas of your image are blown-out—pure white with no image detail in that spectrum to work with. The material between the left and right sides are midtones. A “good” (or, really, a workable) image will show a fairly even distribution of tones across the histogram.

Adjusting the histogram sliders and highlights slider makes this a bolder image.

Just below the histogram are three sliders. The slider on the left is the Black Point slider, the one in the middle the Mid-Tone slider, and the slider on the right the White Point slider. These sliders define how iPhoto should interpret “this is black, this is the center of my midtones, and this is white,” respectively. By adjusting these sliders, you redefine these points and the image then changes.

One of the easiest ways to see this in action is to find an image that has a lot of material in the middle of the image but nothing on either end, indicating that it contains no deep blacks or bright whites. If you drag the Black Point and White Point sliders so that they each touch the place where the graph drops off (thus redefining the black- and white-points) your image will gain more contrast. However, in the process it may get too dark or too light.

That’s where the Mid-Tone slider comes in. Slide it to the left or right and mid-tones are also redefined. As you drag to the left, the image gets lighter as more tone shift right (or to the brighter part of the range). Drag to the right and the image darkens. Play around with these three sliders and you may find that what were once flat and uninteresting images now have new life.

Exposure, Contrast, and Saturation sliders: These three sliders give you finer control over the Lighten, Darken, Contrast, and Saturate buttons that you found in the Effects tab. Shove the Exposure slider to the right, and the image gets brighter. To the left and it darkens. As I explained earlier, the Contrast slider increases or decreases the difference between light and dark areas. And Saturation pumps up or tones down colors. Note that when you move these sliders, the histogram changes. This can help you better understand exactly what the histogram is doing, and what a “good” graph looks like.

iPhoto's Adjust pane.

Below the Saturation slider is the Avoid saturating skin tones option. Enable this when you have an image with a human subject, and you’ll find that their skin tone remains constant while the image’s other colors change as you adjust this slider.

Definition, Sharpness, and De-noise: I gang these three sliders together because they address an image’s detail. Similar though they may sound, they do different things.

You use the Definition slider to add some detail, which generally involves removing “haze” from your image. At its most extreme setting, everything in the image becomes clear. In some cases—with a landscape, for example—this can be great. But impose too much definition on a picture of your dearest and nearest, and you’ll find the results harsh. Regardless of how stunning your subject may be, every portrait needs a little softness.

Sharpness increases the contrast between adjacent elements—for instance, a subject’s hair against their face. As with Definition, at high levels Sharpness can create harshness.

De-noise is an effect that will attempt to smooth out overly pixelated or too-sharpened images. You might use it if you took an underexposed shot (as you might indoors without a flash), pumped up the exposure, and then found that the image was blocky-looking when zoomed in. But overuse it, and you’ll discover that it smears away detail.

Highlights and Shadows: When you first use the Highlights and Shadows sliders, you may believe they were misnamed. For when you adjust them you find that they give you less of the thing you’re adjusting. For example, when you push the Shadows slider to the right, the image’s dark areas lighten. Do the same with the Highlights slider, and bright areas are tamped down.

But don’t let this get in your way of using these two sliders. They’re very helpful. For example, if you’ve taken a shot where there’s a bright light behind your subject (and they appear gloomy in comparison), adjusting the Highlights slider reduces the glare in the background, helping to bring your subject to the fore. And if your subject is murky, cranking up the Shadows slider can help bring them into the light.

Extreme adjustments with either of these sliders may produce a “halo” effect around your subject, where they’re unnaturally separated from the background. So use each slider judiciously and in tandem with Exposure, Contrast, and histogram adjustments.

Temperature and Tint: I talked earlier about adjusting an image’s temperature between the blue and yellow extremes. You’ll find you can do this in the Adjust pane with the Temperature slider. Additionally, you can make adjustments between purple and green hues using the Tint slider.

But you can save yourself some work by relying on the Eyedropper tool found next to the Tint slider. Click it and then click on a gray or white area in your photo. This tells iPhoto “This is what I consider a neutral color. Adjust all other colors accordingly.” When you do this, iPhoto makes its calculations, and the Temperature and Tint sliders are automatically moved based on the results of those calculations. This won’t produce a perfectly balanced image, but it may put you well in the ballpark.

About black and white

No, I haven’t forgotten that I was going to address the task of converting images to black and white. Again, there’s the Pro Way, which requires better tools; and the iPhoto Effects Way, which can sometimes generate unimpressive results. But now that you’re aware of the Adjust pane’s capabilities, I can talk about a third way—The Manual Method. Though not as complete as the Pro Way, it’s a hefty step better than the one-button method.

iPhoto’s one-click black-and-white (left) and manual adjustments (right).

In the Adjust pane uncheck the Avoid saturating skin tones option if it’s enabled. Drag the Saturation slider all the way to the left to remove the color from your image. Now, start sliding those sliders. Begin with the histogram’s Mid-Tone slider to get a reasonable overall balance. Then play a bit with the Contrast slider. The Highlights slider can help your subject pop forward if it’s overwhelmed with a bright background. And finally, work with the Temperature and Tint sliders. Although your image has no colors, these sliders still have an effect on the gray tones of the image. With a little mucking about, you’re likely to come up with something better than iPhoto could manage in an instant.

Beyond iPhoto

As I’ve more than hinted, iPhoto is not the end-all, be-all of image editors. You’ll find more powerful tools in the form of Apple’s own Aperture, Adobe’s Lightroom and Photoshop Elements, and such third-party applications as Pixelmator and Acorn. But iPhoto is easy, it produces decent-and-better results, and—because it’s bundled with nearly every Mac—it’s likely sitting in your Dock, ready to rock.

Next week: Creating iPhoto projects

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