I am currently on my third copy of a particular lens; one of the Sigma ‘Art’ series. Incredible build on this lens coupled with all-round solid performance across the entire zoom range. Remarkably, the lens is able to stop down to f1.8 (despite being a zoom). You can appreciate the criticality of this under low-light conditions – or simply to give yourself some extra freedom on shutter speed. On its day, it’s so good, it’s an absolute must-have. But, therein lies the problem; not every day is its day.
Solid as these lenses can be, it’s no news that they often suffer from severe focusing issues. It’s worse because the problem is hardly consistent. The same lens could be back-focusing at one focal distance and front-focusing at the next. You’ll need NASA-grade algorithms to keep track and be accurate with every shot. I’ve compiled a few alternative steps for those like me who are not too keen on the NASA route. Feel free to combine any or all to achieve even better results.
#1 Re-Calibrate the Focus
As the saying goes, ‘prevention is better than cure’. In this case, prevention is a million times better and less embarrassing than cure (which, in all honesty, is never really guaranteed). If you recently just got your hands on any of the new Sigma Art lenses, you may want to do a quick/crude test for possible focusing issues. Right out of the box, take 4-6 shots of a non-moving target. (I assume a good hand-holding technique; otherwise, use a tripod). Next, view the pictures on the camera display and zoom in to check for details. If the stars align, you should expect to see consistent focusing across all the images. I’m silent on sharpness, because that largely depends on how you’ve set the camera.
If the pictures are markedly different and/or out of focus when you zoom in, there’s a 9 in 10 chance that your worst fears are real. You could immediately return it (depending on the return policy of the shop you bought it from) or have it exchanged. But what are the odds of getting one without that much-advertised issued? You can as well opt for a different brand altogether. But if you’re bent on making the old one work, you should probably invest in a Sigma USB Dock, Calibration Kit and follow Kushagra K‘s walk through.
#2 Do the ‘Multi-Tap’
One trick I use pretty often while shooting is to ensure I take each shot about 3 times (what I call ‘doing the Multitap’). It can drastically increase chances of getting the right one. Even the most reliable technology still can’t be perfect. Sometimes, the flash won’t fire. And the subject my blink or wince. So, 3x.
Once, though, I found myself shooting a major event with one of the Sigma Art Series. I hadn’t had the time to re-calibrate it. And, the venue just naturally ‘picked’ the lens; the extra stop of light, the zoom range, the focusing speed,….. Just about everything, really.
I ended up taking each shot about 6 times just to improve the odds. Guess what, everything turned out great. Client is deeply pleased. [High-risk move. Russian Roulette. Don’t try it at home 😉 ]
Of course, with #2, there can be absolutely no certainty of getting the shot right – given even 8 or 10 tries. Blind gamble (that should only be taken if unavoidable). Photoshop can, however, make the pain a little more bearable. This is all the more relevant where you have shots that are ‘not quite there’ (80-90%; not tragic as per being illegibly out of focus). You can (and should) use it to eliminate as much as possible of the blur and (re-) introduce as much detail as you can.
Here’s something you can do if, after getting through whatever your typical initial post-processing workflow is, you still feel the focus on the image should be sharper. Duplicate the actual image layer and apply a High-Pass Filter (Filter>Other>High Pass). Move the slider left to right until the details you’d like to see just begin to show up (anything more is certain to ruin it). Then press OK. Next is to set the Masking Options (still on that layer). Head to the panel on the right under Adjustments and Layers. Change from Normal to Soft Light. Soft Light, Overlay and Hard Light; that’s the order of aggressiveness. So, you’d want to start easy.
Quick Tip: Multi-tapping is going to take a toll on you flash batteries and memory card space. You’d want to pack adequate backup.