If you shoot digitally or you scan, at some point you’ll need to learn how to properly sharpen your images. It’s important to understand WHY you need to sharpen digital images. Any digital capture process will introduce some softness or blurring to your images. The sharpening that you do in your photo software is designed to replace the original sharpness that you lose during capture and nothing more. Software sharpening should NOT be used on a photo that is out of focus. If a shot is out of focus, it is out of focus–period. No amount of work in something like Photoshop will magically make the image appear to be in focus.
Let me say it one more time. If your images are out of focus to begin with, don’t expect Photoshop, Aperture, or anything else to fix them.
Also, note that the old standard of sharpness was that you couldn’t have a photo that was too sharp. That’s no longer true. Look at published photos. Not every photo needs to be sharp edge-to-edge. Sometimes, you want to sharpen just a certain area of a photo to draw the viewer’s eye to a specific part of the image. Sometimes you won’t care how sharp the photo is at all. Many photos that are not sharp sell well.
Your sharpening technique can help tell your story. Creative sharpening is one more way you can add your unique vision to the photographic process.
There is one other thing to consider if you use a digital camera. Many of the new digital cameras have built-in sharpening routines. Unfortunately, they are typically not effective. They offer the user very little control and sharpen everything in the image. I turn off all in-camera sharpening. Trusting a 19-cent EPROM (Erasable Programmable Read Only Memory) chip in the camera rather than a $650 software program like Photoshop just doesn’t make sense.
You can use unsharp mask, edge sharpening or high pass filtering in most photo applications. You can also use a third-party plugin like Nik Sharpener Pro. Whatever method you use, I strongly suggest that you sharpen last, and that you sharpen with print size in mind.
Sharpening last is important because sharpening should ONLY be applied relative to size and output media. For instance, if you plan on sharpening an image for the Web, and you get it just right, applying that same level of sharpening to a print will usually yield less than perfect results. Applying sharpness to a print that is destined to be printed 5″x7″ on a desktop printer will require different sharpness settings than one destined to be printed 16″x20″ on the same printer. Lastly, the type of media you use i.e., canvas v. glossy paper v. matte paper may have some impact on your decision to sharpen or not – and by how much.
One of my pet peeves is the perpetuation of sharpening formulas on the camera discussion forums. Just because someone can leave a comment in a forum, doesn’t mean they know what they’re talking about. Be careful when listening to this stuff. And to put a finer point on it – let me say point blank, that there is no way that anyone can give you a standard formula for Unsharp Mask, or any other sharpening tool. There is no way to say that every photo will need the exact same amount of sharpening. Without knowing the input and output size of your photo, and what output method you are using (screen or print), and without knowing the subject (a portrait needs less sharpening than an architectural or product shot) there is absolutely no way to know how much sharpening your photo needs. It would be better for you to learn the particulars of sharpening tool you use and experiment on your own.
Don’t sharpen for the pixel peepers. Their electron microscopes will always find SOMETHING wrong with your photo. Pixel peepers don’t buy photographs or typically get jobs publishing them. Your goal should be to sharpen the exact amount necessary for the average photo viewer to appreciate the image, but not so much that the viewer can tell where or how you sharpened.