Fauxmaha
Consider this a preliminary review. Ill update it as things evolve. When I first got this lens, I went out and took a variety of photos in a variety of conditions using my D810. The photos did not have the sharpness I was expecting based on my experience with the outstanding Sigma 50mm Art lens I have been using. Even a casual inspection of the photos showed severe front-focusing. I tried connecting it with my Sigma USB port device (purchased 11 months ago when I got my Art 50mm), but learned that the USB device was now dead. I had only used it once, back when I first received my 50mm. Got the focus dialed in then, and havent used the USB device since. I dont know if the 24mm somehow killed the USB device, or if it just died on its own over the last 11 months, but it was dead. The particular symptoms were that I could plug it in, the on-computer software would recognize it (little green "port" light on screen would come on), but the on-device indicator light would not come on and no functionality was accessible. Called the (very helpful) people at Sigma, talked through the issue, and they concluded there was no option but to send it (the USB device, that is) in for warranty service. As of this writing, it is off at Sigma. I am told they have a 48 hour turn-around in their warranty department, so I expect it back any day. I decided to try the on-camera AF fine tune to see what I could get out of this lens. See the attached photo. I discovered that my subjective conclusion of front focusing was correct. I also discovered that the extent of the front focusing was so extreme that even at the limit (20 units) of the cameras adjustment, there was not quite enough to cure the problem. My intention is to wait until I receive the USB device back from Sigma and then try that. Hopefully I will be able to get these focus problems resolved. If not, I will be quite disappointed. I have had amazing results with the 50mm Art from Sigma, and was really hoping to get similar results from the 24. For now, Im calling this a "Three Star" review. Depending on how things turn out, I expect it will either go to "One Star" or "Five Stars". Update #1: I received my repaired USB dock back from Sigma today. By all appearances, they just replaced it, but either way, the dock now works perfectly with my 50mm, but it still does not connect to my 24mm. I am sending the 24mm back to Amazon for replacement. Well see if the replacement lens solves the problem. Update #2: I received my replacement 24mm from Amazon yesterday, and spent several hours working through focus calibration in my studio. My initial reaction is disappointment. The prior problems with connection to the USB dock are resolved, but so far I do not find this lens living up to the reputation of the 50mm. Not by a fair amount. The sharpness is just not there. Im going to run some more tests, but unless things turn around, this one is going back. Update #3: Decided to try the lens out on a shoot. Took a few hundred action shots in a martial arts environment. Overall performance was better than I expected. Im not a real technical guy, so I dont know about all the details. My "by eye" conclusion is that if you stop this lens down to at least f/4 it becomes acceptably sharp. Wide open? Not so much. My final conclusion is that I am going to keep it, but that it does not have that "magic" that the 50mm ART delivers. The 24 is an "ok" lens.