Design

The 50mm F1.4 DG HSM uses essentially the same cosmetic design as its 35mm F1.4 sibling, but is slightly larger in size. The majority of the barrel exterior is made from high quality plastics, with a shinier metal section immediately adjacent to the mount. A small inlaid silver plaque with the letter 'A' denotes that it's part of Sigma's high-end 'Art' line. There's really nothing to complain about here in terms of fit and finish, which feels excellent. One possible concern, depending on your needs, is that the lens isn't weathersealed; but then again, few of the alternatives are, either.

The broad manual focus ring occupies the front of the barrel, and turns smoothly; it doesn't rotate during autofocus, which is always welcome. Focus is fully internal, meaning that the front element doesn't move during the process. The auto/manual focus mode switch on the side of the barrel is unusually generously-sized, and a large section of the barrel's underside is ridged to provide a positive grip when changing lenses. These small touches help make the lens a pleasure to use.

Design and specifications compared to other similar lenses

The 50mm F1.4 Art is quite different from any previous autofocus 50mm F1.4 for full frame, and much more similar in size and optical design to a typical 35mm F1.4 lens. This means it's almost twice the length, and three times the weight of the more traditional double-Gauss designs from Canon and Nikon. It's also substantially larger than either the older Sigma 50mm F1.4 EX DG HSM, or the Sony Carl Zeiss Planar T* 50mm F1.4 ZA SSM, both of which are pretty sizeable for a 'fast normal' prime.

Here you can see how much larger the Sigma 50mm F1.4 is compared to a traditional design the Canon EF 50mm F1.4 USM. For some potential buyers, this extra bulk may be reason enough to discount the Sigma.

The table below compares the Sigma's key specifications to other 50mm F1.4 primes, and the $4000 Zeiss Otus 55mm F1.4 to which it's widely been compared. The key point to understand is that it's the second-largest and heaviest lens here by quite some margin. It's not as huge as the Otus, but it's about twice the length, and nearly three times the weight of Canon and Nikon's more traditionally-designed 50mm F1.4 lenses.

 
 Focus  AF  AF  AF  AF  AF  Manual only
 AF motor  Ring-type
 ultrasonic
 Ring-type
 ultrasonic
 Micro-type
 ultrasonic
 Ring-type
 ultrasonic
 Ring-type
 ultrasonic
n/a
Minimum focus  0.40m  0.45m  0.45m  0.45m  0.45m  0.50m
Max magnification  0.18x  0.14x  0.15x  0.15x  0.14x  0.15x
 Filter dia  • 77mm  • 72mm  • 58mm  • 58mm  • 72mm  • 77mm
 Weight  815g
 (1.80 lb)
 505g
 (1.11 lb)
 290g
 (0.64 lb)
 290g
 (0.64 lb)
 518g
 (1.14 lb)
 970g
 (2.14 lb)
 Diameter  85mm
 (3.3")
 85mm
 (3.3")
 74mm
 (2.9")
 74mm
 (2.9")
 81mm
 (3.2")
 92mm
 (3.6")
 Length  100mm
 (3.9")
 68mm
 (2.7")
 51mm
 (2.0")
 54mm
 (2.1")
 72mm
 (2.8")
 141mm
 (5.5")
 Weather-
 sealing
 • No  • No  • No  • No  • Yes  • No
 Available  mounts  • Canon
 • Nikon
 • Sony
 • Sigma
 • Canon
 • Nikon
 • Pentax
 • Sony
 • Sigma
 • Canon  • Nikon  • Sony  • Canon
 • Nikon

The take-home message is that if you're considering upgrading to the Sigma from one of the camera manufacturer's 50mm F1.4 primes, you're going to have a accept that it's a much bigger beast to carry around with you.

Click here for a more-detailed specification comparison between these lenses

On the camera

The Sigma is a pretty large lens, indeed it's the heaviest and physically longest of all autofocus 50mm F1.4s. Despite this it balances well on larger SLRs, and is perhaps most at home on mid-size bodies. Above we're showing it on the full frame Canon EOS 5D Mark II (left), and the APS-C Canon EOS 70D (right). On smaller APS-C SLRs like the Canon EOS 700D, the overall balance shifts much more towards the lens itself. But with a normal grip supporting the lens with your left hand, this really isn't a problem.

Autofocus

The 50mm uses Sigma's Hypersonic Motor for autofocus, which is very quiet indeed. For normal eye-level shooting we've found our Canon-mount copy to perform pretty well, offering fast and positive focusing. When using the central AF point we've seen no evidence for systematic focus errors on test bodies ranging from the entry-level EOS 100D to the top-of-the-line EOS-1D X, but accuracy and consistency deteriorates with outer AF points, especially with lower-end bodies. As always, it must be noted that focus speed and accuracy is dependent upon a number of variables, including the camera body used, subject contrast, and light levels.

Switch from the optical viewfinder to live view, though, and the story get more complicated, depending on the camera used. We found that the lens works very well with the Canon EOS 70D and its (currently-unique) Dual Pixel AF, providing fast, accurate focusing that's also much more reliable when using off-centre AF points. This is great news for 70D owners, but less helpful for anyone else right now.

For users of cameras that rely on Hybrid or Contrast Detection AF, the lens performs somewhat less well. Even on the EOS 100D (which has Canon's best performing live view Hybrid AF system to date), focusing slows down considerably, although it is at least still pretty quiet. However if you refocus during movie recording, the clicking of the AF motor as it fine-tunes focus might easily be audible on your soundtrack in quieter conditions.

Lens body elements

The lens comes in Canon, Nikon, Sigma and Sony versions; our review sample was in the Canon EF mount.

One point worthy of note is that there's no rubber seal around the mount, or any other specific claim of weathersealing.
The filter thread is 77mm (which is large for a 50mm F1.4) and, as a result of the lens's internal focus design, it doesn't rotate on focusing. This means filters such as polarisers and neutral density gradients are much easier to use.
The bayonet-mount hood is provided as standard, and clicks positively into place on the front of the lens. It's made from thick plastic, and features ribbed moldings on the inside to minimize reflections of stray light into the lens. Sigma has even added a ribbed grip to make it easier to remove.

A discrete grey mark aids alignment for mounting, and the hood reverses neatly for storage.
The focus ring has a 25mm-wide ridged rubber grip, and rotates 90 degrees clockwise from infinity to 0.30m, matching Canon and Sony lenses but opposite to those from Pentax and Nikon. Its action is nice and smooth, and it doesn't rotate on autofocus.
The lens has a basic distance scale, with depth-of-field indicators for the minimum aperture of F16 only. Note that these are calibrated for use on full frame cameras; on APS-C the extremes of the indicated range won't appear as sharp.

We're not hugely convinced by the grey-on-black markings for feet, which can be difficult to read in less-than-perfect light.
The large, positive focus mode switch is prominently placed on the side of the barrel. When set to AF a white inlay is visible behind it; switch to MF and the other side is black. This provides a quick visual cue to confirm the focus mode, that's easier to see in dark conditions.
A generous 30mm-wide ridged grip covers most of the underside of the barrel, and provides positive handling when changing lenses.

The '014' denotes the lens's year of release. Sigma apparently envisages that this will become akin to the vintage of a wine, with each future 50mm F1.4 likely to have a different balance of characteristics (and crucially, not necessarily being 'better' or 'worse').

USB Dock compatibility

The 50mm F1.4 is compatible with Sigma's unique USB dock, a relatively inexpensive accessory (£40 / $59 / €60) which allows you to hook Sigma's latest lenses up to a computer - click here to read our quick review. Using the Sigma Optimization Pro software you can then apply detailed autofocus microadjustments if you find your lens consistently mis-focuses on your camera (which can be something of an occupational hazard for SLR users). There's also an option to update the lens's firmware, if it should become necessary in the future.

When we tested the USB Dock last year, we found the main problem to be the lack of detailed documentation, and specifically any real explanation of how to determine and set autofocus adjustment values. We also suspect that most buyers of the 50mm will be using it on cameras that include AF microadjustment settings in their firmware, which reduces any need to use the USB Dock. Despite this, we're pleased to see that Sigma is offering the option.