First off, let’s discuss two things the sharpening tool won’t help with:
1. Blurry photos due to camera or subject movement. You know the kind. You take a photo and the camera moves during exposure, giving a “wiped out” look to the entire image. Or maybe a frisky child decides to turn away just as you press the shutter and his little head gets all out of focus while the rest stays sharp.
2. Blurry photos due to bad focus. Yup, if the photo is out of focus, no amount of sharpening is going to help. If it’s just a little soft, that can usually be fixed, but full blown, out of focus is beyond what any software can fix—for now.
I know, this begs the question, “Then what use is a sharpening tool if it can’t sharpen blurry photos?”
The tool is there to help bring back the sharpness to a scanned image or digital photo. See, whenever an image is captured digitally—be it with a camera or scanner—it always becomes a bit “soft”. Most cameras and scanners automatically do some sharpening, but they don’t always get the job done quite as well as we might like. So, this tool helps you pick up where they left off.
So, when you go into your imaging software and select “sharpen” (or the Unsharp Mask for Photoshop and similar programs) what happens? Basically, the sharpening tool finds edges and makes them look sharper.
As for using the tool, in most programs it’s fairly straightforward. Normally, there’s a little slider that you move to increase the sharpness. The further over you push it, the more effect the tool has.
Some sharpening tools also include settings for “Threshold” and / or “Radius”. The Threshold setting will determine how much difference between pixels there has to be before that area is sharpened—or before it’s considered an “edge”. Radius is simply how “thick” the sharpness of the edges will be.
How you set your Threshold and Radius numbers will largely depend on your image. Start with lower numbers and work from there. I generally start with my radius at 2 and my threshold at 2 or 3, and then make adjustments until I get the look I’m after.
I’ve also found that while I can get an “average” amount of sharpening, there’s not a “one size fits all” setting that works. It really depends on the camera, lens, and subject. Some subjects need very little sharpening, while others require more work.
Also, keep in mind that sharpening should generally be about the last step when you’re processing an image. Take care of the colors, contrast, resizing, etc, first – then sharpen.
Finally, don’t oversharpen your images. It’s always tempting to sharpen the heck out of ‘em, but resist that temptation with all your might – even if it requires your left hand to pull the mouse from your right. Try to make the photo look real—remember in real life there aren’t any sharp “halos” around the edges of objects
Here are some sample shots that apply what we’ve talked about:
First off, here’s an image I took a couple weeks ago without any sharpening. This is the way it was out of the camera (also, the camera was set not to sharpen):
Next, here it is after—what I feel—is about the proper amount of sharpening:
Now, here it is oversharpened. Notice the “halos” starting to form around the sharp edges:
Note the JPEG compression adds a little jaggedness to the edges (especially since these are low res picts), but you get the general idea