Dave Stevenson
Sharpening tools can go some way to correcting images, but the only way to ensure spot-on photos is to take a decent shot in the first place.
If there’s one thing photographers are likely to be obsessed by it’s image sharpness. Most defects with an image – missed exposures, dodgy composition, even unwanted objects and entire people – can be rectified after the fact. Sharpness doesn’t fall into that group. Sure, every piece of photo editing software between Picasa and Photoshop has a tool for adding sharpness, but the job of creating magical tools falls to Steve Jobs’ marketing department.
Sharpening tools are designed to work within fairly tight tolerances to correct relatively tiny errors caused by lenses working at their optical limits and diffraction. If you’ve got an image that has motion blur, or simply isn’t focused properly, a sharpening tool won’t bring it back. It’s only if you have an image that’s focused properly but is let down technically by a fault somewhere else that a sharpening tool will really be able to help you.
Take this image of a blue tit. While any shoot produces more hits than misses, this is one of a series of high-speed shots, and it’s not surprising it’s out of focus. Even with a top-end lens and DSLR body, mechanics and computers can only do so much, and even the best autofocus system is going to wander off track occasionally. While it would be useful (to say nothing of indecently profitable) to have a sharpening system that could retrieve this shot, nothing of the sort exists. That’s to say that the best way of getting a sharp shot, bar none, is to take a sharp shot. Focus carefully, make use of your camera’s autofocus points, if you have them, and use the fastest shutter speed you can to freeze the action in the frame.
The image of a pair of flamingoes tussling for food is an entirely different kettle of fish. It’s more than sharp enough to print, and whatever lack of edge definition the image suffers from is due to the overwhelming number of factors that can render an image slightly soft – camera shake, the effect of the DSLR mirror moving quickly and the shutter firing, imperfect glass in the lens, or simple atmospheric haze and distortion. This minor lack of sharpness can be effectively compensated for afterwards when the Raw file is processed, and while it won’t make much difference to the shot as viewed on a screen, the difference in print will be significant.
Still, as someone who’d rather not see countless images ruined by cack-handed editing, it’s important to remember that sharpening has its limits – a series of traps designed to trip up careless editors and make photographers look silly. Yank the sharpen slider too far, and edges that should gradually increase in definition will start developing bizarre, unnatural halos, giving your image a strange, half-watercolour, half-computerised look that will make it appear as if you attempted to chisel your photo onto a block of polystyrene using a blunt butter knife and a sledgehammer.
This was underlined clearly to me the other day when I sent a lovely monochrome file off to the printers, only for it to return a total mess. Instead of the silvery-smooth, timeless look I’d achieved the first time I’d printed it (before losing track of the edited final version and hurriedly re-editing the original file), I got a weird mess of new textures and ruined brightness. Indeed, the final effect was so disturbing and unusual that, outraged, I hurried to check the file I had used to print from to make sure that the printers hadn’t done something appalling in the intervening time.
They hadn’t. Over-enthusiastic sharpening and a rare failure to check my work before sending it had resulted in a ruined print – luckily, a print intended for proofing rather than some huge and expensive A2 giclée effort for my (or, worse, someone else’s) wall.
There are two morals to the story. The first is to always check your work. As a rule, I’m opposed to what photo nerds everywhere call ‘pixel-peeping’ – the act of inspecting a photo so closely you lose track of what it’s actually of, in the name of discerning miniscule imperfections. However, images for print show their imperfections so readily – and unexpectedly – that at the very least every image you send should be checked at 100%. You don’t need to fetishise the removal of problem areas – no-one looks at a picture on a wall from half an inch away – but new, unintended textures and dust spots will be obvious and permanent in print. Just remember that after a point, sharpening begins to use computer-generated detail that obscures detail in the original frame.
A second piece of advice follows last issue’s column if you have to apply boatloads of sharpening repetitively to a series of images, it may be time to upgrade the lens that came with your camera. My belief remains that a good image is made at the time you fire the shutter. Sharpening and more reliable alterations such as exposure correction need to be applied with a light touch if you want your prints to look as good as possible. And, as my A level tutors apparently failed to drum into me all those years ago, always check your work.
