Sharpening Strategies

First things first: iPhoto can't take a blurry photo and make it tack-sharp. No digital imaging program can, regardless of what you see on TV. If your subject is out of focus or blurred, it's going to stay out of focus or blurred.

So why have a sharpening feature? Because all digital imageswhether captured by a scanner or a camerahave an inherent softness. Some softness is introduced by inexpensive lenses. Still more is introduced by imaging sensors and their fixed grid of pixels.

Digital cameras compensate for this inherent softness by applying some sharpening immediately after you take a photo. You can often adjust the amount of sharpness they apply; I like to turn down the sharpness settings on my cameras, preferring to sharpen later, if necessary. (If you shoot in raw mode, your camera applies little or no sharpening to the image; see page 154.)

Inkjet printers and offset printing presses (including the kind used to print iPhoto books, greeting cards, and calendars) also introduce some softness. The bottom line: several factors are working against your image to obscure fine details.

And that's where sharpening can help. By sharpening a photo just before printing it, you can often get a much better print.

Sharpening is a serious form of image surgery. There are right times and wrong times to do it, and it's easy to introduce ugly visual artifacts by sharpening at the wrong times. Here's how and when to sharpen up.

Sharpening Basics

To sharpen a photo, drag the Adjust panel's Sharpness slider to the right.

Before Sharpening

After Sharpening

How it Works

iPhoto uses a sharpening technique called unsharp masking. The term derives from an old photographic process. In the digital world, unsharp masking works by increasing the image contrast between light and dark pixels. iPhoto detects boundaries of light and dark, and it makes light edges a bit lighter and dark edges a bit darker. When it's done rightthat is, not to excessour eyes perceive this as increased sharpness.

Sharpening Tips

Should You Sharpen?

Just because digital images have an inherent softness doesn't mean that you should apply sharpening to every photo you take. First, consider the photo itself. A photo that lacks fine detailssay, a close-up of a baby's facewon't gain much from sharpening, and may even be hurt by it. Conversely, a photo containing fine detailssuch as the one on the opposite pagemay benefit greatly from sharpening.

Also consider how you'll be using the photo. A photo destined for an iDVD slide show or iMovie HD project probably doesn't need sharpening. A photo that you plan to printeither yourself or by ordering prints or a bookis a better candidate for sharpening, especially if the photo contains fine details.

Sharpen Last

If you remember one tip about sharpening, remember this one: sharpening should be the last step in a photo-correction session. If you crop, straighten, retouch, or otherwise modify a photo after sharpening it, you risk ugly visual artifacts.

If you're performing numerous edits in one sessionfor example, you open an image in edit view and then do some cropping, straightening, exposure tweaking, and sharpeningiPhoto applies some built-in smarts when you click the Done button. iPhoto applies your edits in a sequence that optimizes quality, and that process includes applying your sharpness settings as the very last step before saving the edited photo.

But if you're like me, you sometimes perform edits in multiple passes. You might crop a photo, then save it and email it to a friend. Then, you might return to it for some exposure tweaking.

If this describes your working style, avoid applying sharpening unless you know you won't be doing any further edits. If you think you might need to edit the image again, make a duplicate ( -D) before sharpening, and indicate in the duplicate's title or comment that it's a pre-sharpened version.

(For more advice on developing an iPhoto editing workflow, see page 153.)

When in Doubt, Duplicate

The only way to remove sharpening from a photo is to revert to the original versiona step that also discards any other edits you've made. For this reason, it's a good idea to duplicate a photo before sharpening it.

View Right

iPhoto's edit view introduces some softness of its own when it scales a photo to whatever zoom setting you've made. To get the most accurate on-screen view possible, view your photo at 100 or 200 percent when making sharpness adjustments: press the 1 key to view at 100 percent, and the 2 key to view at 200 percent.

Printing? Sharpen Heavily

Don't be afraid to heavily sharpen a photo that you're going to print. Even if the photo looks a bit too sharp on screen, chances are it will print nicely. When I'm creating 5- by 7-inch or larger prints on my Epson inkjet printer, I'll often crank the Sharpness slider all the way up to 100 (after first duplicating the photo, of course).

Also consider the paper you're using. Premium glossy photo paper shows fine details best, so photos destined for it can benefit from sharpening. On the other hand, matte- and luster-finish photo papers have a fine texture that obscures detail a bit.

Blurring a Photo

Sharpening cuts both ways. You can also blur a photo by dragging the Sharpness slider to the left of its center point. If you have a noisy photo shot at a high ISO setting (see page 212), try introducing just a bit of softness to reduce the digital noise.

Or soften up a photo to create a special effect. You can create a lovely background for a video title or DVD menu by blurring up a photo and optionally adjusting its brightness and contrast (see page 301).