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benveniste

July 2017

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[personal profile] benveniste

The Sigma 24-35mm lens is the first f/2.0 zoom lens which is designed for use with a "full-frame" digital camera or 35mm film. For over a decade, my wide angle lens was a Tokina 24-40mm f/2.8 manual focus lens, and was quite happy with it. But when I finally got around to upgrading to an autofocus camera, I decided I wanted something a bit wider. I eventually ended up with a Nikon 17-35mm f/2.8D. So in some ways the smaller zoom range of the Sigma was a bit of a nostalgia trip for me. I decided to try one, but instead of buying it outright I rented a copy from lensrentals.com. In all, I'm glad I did. While Sigma seems to have done a nice job with this lens from a technical standpoint, and it should appeal to a couple of different audiences, I don't think I'm in either one.

Physically, the lens is slightly bigger and almost 200 grams heavier than the 17-35mm. So realistically, the reason to buy this lens is for the extra stop of speed offered by the f/2.0 aperture.

Size comparison

Zoom Range


With that in mind, I did most of my informal testing with the lens wide open. To illustrate the available range, here are three "beachscape" shots at 24mm, 28mm, and 35mm.

24mm:
24mm

28mm:
28mm

35mm:
35mm


While I can't think of too many scenarios where I'd plan to carry 24mm, 28mm, and 35mm prime lenses, I think it's reasonable to think of this lens as replacing the two primes at either end of the range. These shots also show that there is quite a bit of light falloff towards the edge of the frame at f/2 at all focal lengths. They show nothing about sharpness, though, especially since my D800 found different AF solutions for each shot.

Sharpness and Contrast


The first potential audience for this lens are technophiles drawn by the allure of a technical first. That audience also tends to be more demanding in terms of the optical performance. A couple early adopters reported issues with front focus, so I elected to perform AF fine tuning before proceeding, using both a LensAlign device and contrast comparisons to Live View. I eventually "landed" on a +12 setting, indicating moderate but correctable front focus. Settings for other lenses in my arsenal range from +7, through 0, to -4. It'll be interesting to see if a trend develops.

Since I was right next to my copy stand, I decided to start with a decidedly "off-label" test. This is not a lens one would normally choose for photographing documents, let alone wide open at f/2, but it turns out to give some insights.

35mm:
Full Shot
100% Crops:
Center
Top
Corner



24mm:
Full Shot
100% Crops:
Center
Top
Corner

The first thing one notices is distortion. At 35mm, the pincushion distortion is likely acceptable for all but the most technical targets. However, the barrel distortion at 24mm is quite significant. In the center, resolution is very good at all focal lengths, but there is a noticeable drop off towards the edges, and the corner resolution at 24mm shows evidence of field curvature and overall softness. If you're looking for a "test chart hero" at short range, this isn't the lens for you. More realistically, if you're setting up a "forced perspective" shot with an off-center foreground image, be prepared to stop down quite a bit.

Next comes "ye olde brick wall test." Since it's an old mill town, Lowell Massachusetts has a lot of brick walls. I picked one pretty much on the basis of available light. At this more typical shooting distance, both the distortion and field curvature were less pronounced. Here are the 24mm results; I also have a shot at 35mm, but I really don't mind if you sit that one out.

Full Shot
100% Crop -- Top Left Corner:
Top Left Corner

There was also a request for a wide subject shot at distance. For that, I decided on a train:
Train24
Train35
The NEF's for these files are here and here. Other NEF's available on request.

I freely admit that I find sharpness overrated as a criteria for judging lenses. If you're consistently shooting from a tripod using live view and looking to get the last quantum of sharpness out of your camera, you're better off with a pair of f/1.4 primes than this zoom.

Subject Isolation and low-light performance


The second potential audience for this lens are those who wish to use f/2.0 to control depth of field and in low light. Here's a "shot of opportunity" which I feel shows that even at f/2.0, a longer lens is a better choice to achieve subject isolation. While Lowell MA does boast a few historic locks, I don't think they mean these:

Locks

While I did observe a bit of the "swirly bokeh" reported by Zach Sutton, my subjective call on the bokeh is that it's a solid step better than the 17-35mm f/2.8.

Here's what I grabbed for a low-light test (Uncorrected and corrected for perspective). It's one of the few times I missed having a wider (or PC) lens. It's pleasing, but I was unable to generate any significant starbursts, perhaps because of the minimum aperture of f/16.
Uncorrected
Corrected

Filters


Like Nikon's new 24-70mm VR, this lens accepts 82mm filters. This poses a hazard to Nikon user's wealth. I do own one 82mm filter, which is a generic 82mm Opteka circular polarizer. (It claims to be multicoated, but I see no evidence of that). Even though it's about 7mm thick, I see no evidence of vignetting with this lens at 24mm.

Conclusion


This is an impressive achievement by Sigma. Not only have they proven that an f/2.0 zoom is feasible for "full-frame" digital, but they produced a lens with very-good if not world-beating optical performance at a $1000 price point. While the lens is heavy, I felt it balanced well on the D800 body and I had no concerns about using the camera's tripod mount. But I sent it back to the rental agency without any real regrets. I'd rather have the extra width of the 17-35mm f/2.8 Nikkor than the extra stop of the 24-35mm f/2.0 Sigma. My 17-35mm is a 16-year old design which could use an update. Nikon does offer an extraordinary 14-24mm f/2.8 lens and has just introduced a new 24-70mm f/2.8 VR. So perhaps they feel they don't need to spend R&D resources on an "in between" professional-grade zoom. Too bad.

The more interesting question is "what's next." Will Nikon and Canon respond to Sigma and start producing f/2.0 zooms of their own? Will Sigma extend their product line with an f/2.0 portrait zoom? While I hope to follow such developments in the coming year, for now my credit card is safe.
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