Sent to you by David via Google Reader:
Ideally all of your digital photos would turn out crisp and clear every time; unfortunately that's not always the case. For those times they don't, this beginner's guide to sharpening your images in Photoshop is a good place to start.
Photoshop pro Helen Bradley goes into depth with Photoshop's Unsharp mask (this tool is available in other alternative image editors, too, including GIMP) to achieve the digital equivalent of an old darkroom trick:
In the darkroom the process is achieved by taking one negative and a slightly blurred positive image, sandwiching these together and making a very quick exposure of this sandwich. Then the exposure is completed using the negative. The resulting image has sharper and crisper edges than it would have had if the blurry (unsharp) mask image had not been used. The typical sharpening tool used in Photoshop and other graphics programs is named after this traditional darkroom process and is called the Unsharp mask.
We've covered this territory once before, but now that everyone's pulling out their cameras to capture those summer vacation memories, it's not a bad time for a refresher.
Update: A knowledgeable reader writes in with his two cents:
Hey, just dropping a line to suggest that Unsharp Mask is actually a very imprecise sharpening solution. It should be avoided like the plague in almost every application. In my time as a photo archivist I have learned this the hard, mildly-embarrassing way. The main problem is that it sharpens highlights and shadows in equal measure, so it's quite easy to get HEAVY artifacting (the mark of this very-old tool is a "halo" effect around shapes) even when you're not doing a ton of sharpening.
A night-and-day better tool is Photoshop's own Smart Sharpen, in the advanced settings mode. It grants you the ability to roll off all the sharpening on highlights, so that it's only actually sharpening the shapes in the image. It also lets you roll off the sharpening on the shadows, which allows you to avoid excessively sharpening edges or surfaces (and helps you avoid sharpening film grain rather than the image itself). You can do much more sharpening this way without exponentially increasing the image's noise. Smart Sharpen does take a bit more time to work its magic for the complicated math it uses, but it's a pretty brilliant tool and one of hundreds of reasons Photoshop has no real competition right now.
If you're just sharpening your MacBook headshots for facebook, by all means enjoy your unsharp-masking. But if you're working with any picture that you really care about, do it a favor and sharpen smartly.
P.S. To the commenters - "Smart Sharpen" IS in fact a high- (and low-)pass sharpening method. Any more intricate/complicated high-pass methods won't get you any better results than Smart Sharpen.
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