The Sigma 17-40mm F1.8 DC Art for L-Mount is an APS-C zoom with a constant F1.8 aperture, covering a 25.5-60mm equivalent range. On full-frame L-Mount bodies it is used in APS-C mode, which suits video well, since many of these cameras shoot in a Super 35 crop anyway. It also suits Leica CL and TL2 owners, who use it on the full sensor.
Image quality
Inside are 17 elements in 11 groups, including four SLD and four aspherical elements, which keep it sharp and free of obvious colour fringing at F1.8 across the whole range. An 11-blade rounded aperture gives smooth, round background highlights, and the front element has a water- and oil-repellent coating that makes it easier to wipe clean.
Built for video
The zoom is internal, so the lens keeps its length and balance on a gimbal, and focus breathing is kept low. Sigma's HLA linear motor gives fast, quiet autofocus. The L-Mount version also works with Sigma's USB Dock UD-11, which lets you update the firmware and change how the manual focus ring responds, choosing a linear setting for repeatable focus pulls.
Handling
Two AFL buttons sit on the barrel for landscape and portrait holds. The lens is dust- and splash-resistant, the front element has a water- and oil-repellent coating, and it takes 67mm filters.
Who it's for
This is for L-Mount video shooters using the Lumix S5II, S1H or Sigma fp in Super 35 or APS-C mode, and for stills shooters with a Leica CL or TL2. On a full-frame body in crop mode a 24MP sensor gives roughly 10MP stills, so for full-resolution photos a full-frame lens such as the Sigma 28-70mm F2.8 is a better match. If you only need a light walkaround zoom, the Sigma 18-50mm F2.8 for L-Mount weighs 290g.
Also available for Sony E, Canon RF and Fujifilm X.
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