The incredible performance does come at a cost - there are tradeoffs that must be made. The first to be aware of is that it will not work with full frame cameras - if you try you will end up with crazy vignetting in you images and be forced to crop down to an APS-C size image. Secondly, the zoom range is very short - 18-35mm is only a 2x zoom factor, and on APS-C 18-35mm translates to roughly 28-50mm equivalent Full Frame field of view. However, that works out just fine due to the constant f/1.8 aperture and persistently stellar image quality - it's like having a half dozen prime lenses in one - hence it is known as a "bag of primes". Lastly, it lacks image stabilization, but though this is unfortunate it has not been a problem for me, even when shooting handheld video in low light conditions!
I filmed this video entirely hand-held while hiking through the forest. By shooting at 60fps and applying digital stabilization in post production in DaVinci Resolve I had no trouble crafting a smooth and cinematic experience.
This is likely due to satisfying heft of the 18-35 - it balances perfectly on my Canon 80D and is easy to hold steady in my hands. The build quality is very impressive - all metal, tough plastics, and sturdy rubber rings. There is even some weather sealing in the form of a gasket around the lens mount. The lens also focuses and zooms internally, so there is less opportunity for dust and moisture to intrude.
I found the autofocus to have acceptable accuracy and speed, though it's not anything spectacular. It does the job and that's enough for me! It's very quiet, which is helpful when shooting video while recording audio - essential if you are using the camera's internal microphone.
Of course, the most important factor here is image quality, which as I've mentioned is extremely good. When your subject is in focus it's tack sharp, even wide open at f1.8, and the out of focus areas are beautifully smooth. With such a wide aperture it's possible to isolate your subject from the background even at a distance.
Surprisingly, the 18-35 is actually capable of macro photography. It can't get extremely close, but for moderately small subjects it provides excellent quality. An advantage of shooting macro subjects with a wide angle lens is that you can include some of the surrounding environment with them. With that 1.8 aperture you can still ensure that the focus is on your subject while hinting at the bigger picture and putting your subject in context.
Sitting nicely in the $600 - $800 range the Sigma 18-35mm f/1.8 Art is an impressive bargain for the quality and versatility it offers. I have found the claims that this is a "bag of prime lenses" and that it offers full frame results on crop sensor cameras to be totally justified. It is the first lens I will chose for any excursion - the first one I pull off the shelf when packing for a trip. When filming reviews for my Youtube channel this is the lens that will be used. It is a beautiful lens that produces beautiful photos and professional footage, and which I cannot recommend highly enough.
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