Sigma Large Aperture Standard Zoom Lens

I bought this lens when buying a new Nikon D5600 after shooting with an old Tamron 17-50mm F2.8 on an older Nikon DLSR for many years. I chose this lens over buying a new Tamron 17-50mm because I was interested in the faster hyper-sonic focus motor, the optical image stabilization, and just wanted to try something new and different. In the end it’s a decent, sharp lens, but I wish I had bought the Tamron instead. This lens’s weight and dimensions make it only look a bit larger and a bit heavier than the Tamron 17-50mm on paper, but the reality is it feels much bulkier and heavier. This is especially true on lighter DSLRs like the D5600. The focus ring turns as it autofocuses and is coupled to the focus mechanism so if you touch it by accident during auto-focus (which is very easy to do given it’s placement and proportions), the lens produces a high pitched whining sound. I’d imagine that if you held the focus ring from moving during auto-focus for more than a moment it could do some damage. This fact makes its mass feel less like solid construction since you need to be extra mindful of how you handle it. It takes rather large 77mm diameter filters and it’s tulip shaped hood feels like it adds even more volume to the lens when put on backwards for storage than other lenses that I have which came with hoods. The OS (optical image stabilization), doesn’t practically provide as many stops of stabilization as the specs claim. In a few quick tests it seemed to give me 2 stops of help, but certainly didn’t stop me from motion blurring images at 1/15th and below. It also continues to run for a minute or so after shooting or focusing, so if you shoot, then you’re holding the camera, after a minute or two you’ll hear and feel a little knock in the lens as the optical stabilization goes to sleep. I haven’t used this for extended periods or compared with other lenses so I can’t say what its effect on battery life is. It can of course be turned off though. All in all, it’s not as great of a feature as I had hoped it would be. The lens’s images are pretty sharp and have good color and contrast. It can certainly produce good looking still images. The focusing is pretty quick but not silent, the lens makes ticking sounds which are readily picked up by the internal microphone if shooting video. The ticking might also be audible at a low level on a hotshoe mounted mic under some circumstances. I read in various reviews before buying that there were quality variations between copies of this lens and that some have reported a bit of a back focusing issue. I can’t say I notice it when shooting normal subjects in a room or outdoors, but when I focus on close and small subjects, especially when wide open with a shallow depth of field, the actual plane of focus seems a little off from the focus point I used (despite the camera’s AF system thinking it was in focus.) The extra weight, bulk, breakable feeling of the focus ring mechanism as AF works, modest gains from optical stabilization, and slight back-focusing issue altogether make me wish I hadn’t bought this lens and had gotten another Tamron 17-50 f2.8 which I know to deliver beautiful images and a slightly more comfortable weight and size. I'm not enthused to go out shooting with this lens so I will probably get rid of it soon and get something else.