Sigma Art lenses are renowned for razor-sharp detail on the focal plane, even at widest apertures. It seems simple, enough, doesn’t it? If you are buying a very fast aperture lens, you will want to take advantage of the extra light-gathering power, not just for the through-the viewfinder experience, but also for the on-the-sensor feel of an F1.4, F1.8 or F2 aperture, whether in dim lighting situations to keep ISOs low, or simply for the aesthetic that a very shallow focal plane offers and how the foreground and background are rendered.
The laws of optical physics do insist that every lens will be a bit sharper overall when the aperture is stopped down slightly, and the same holds true for Sigma Art lenses. This is most noticeable on test targets, which, honestly, are one of the most boring photo subjects ever. In real world situations, Sigma Art lenses are growing more legendary each day for the total imaging performance this gear delivers, whether wide open, or stopped down a touch.
Now, shooting at the absolute widest aperture on a given lens isn’t always necessary, or necessarily desired, due to the very shallow depth of field, which can be mere centimeters thin when wide open and close-focused; but knowing that the slim focal plane sharpness will be crisp and pleasing when that is what the composition calls for is simply perfect.
A fast-aperture lens that needs to be stopped down significantly to ensure decent image quality just doesn’t make sense any more; and that’s a big part of the optical design philosophy of the Art lenses. These lenses excel at focal plane sharpness, even wide open!
All Sigma Art lenses are able to be tuned with the USB Dock for Microfocus adjustments, which can help improve critical focus to ensure peak sharpness: when wide-open, there’s much less “wiggle room” between the AF sensors and the focal plane. So being able to tweak this in four zones on a prime and sixteen zones on a zoom helps ensure peak performance.
Wide open, or stopped down a little to increase total depth of field and ground rendering characteristics, the Sigma Art lenses, are always incredibly sharp. And in the world of modern digital photography and cinematography, this is exactly what you would and should expect from your fast-aperture prime and zoom lenses.
Jack Howard is a lifelong photographer and author of two editions of the how-to book, Practical HDRI. Based in Central Jersey, Jack's go-to photography spots are backroads and beaches of his home state. He loves to travel far and wide with his wife and daughter, visiting national parks, museums, tropical islands and more along the way.