Sigma 19mm f/2.8 EX DN

SLRgear Review
July 31, 2012
by Andrew Alexander

Sigma announced that it would be providing lenses for mirrorless cameras, and the 19mm ƒ/2.8 DN ("Digital Neo") is the company's second lens to do so. The lens is offered in the micro four-thirds mount offered by Olympus and Panasonic, and the Sony E-mount for the NEX series of camera.

On a micro four-thirds camera body, the lens will offer an equivalent field of view of 38mm; on a Sony NEX camera body, the lens offers an equivalent field of view of just over 28mm (both of these figures are in the 35mm film equivalent).

The lens ships with a round lens hood, takes 46mm filters, and is available now for around $200.

Sharpness
The lens provides sharp images, more so on the micro four-thirds camera than on the Sony NEX, owing to the fact that the micro four-thirds sensor does not "see" the corners of the lens.

Mounted on the Panasonic GX-1 m4/3 camera, the lens produces excellently sharp images even wide open at ƒ/2.8. There's just a hint of corner softness at ƒ/2.8, but even this is all but eliminated by just stopping down to ƒ/4. Stopping down to ƒ/5.6 technically provides more sharpness, but you'd only notice it looking very closely at a test chart. Diffraction limiting sets in at ƒ/8, but you won't notice any impact on sharpness until ƒ/16, where it is still very sharp across the frame. Fully stopped-down at ƒ/22, there is some impact on sharpness, but it's still very good.

Mounted on the Sony NEX-7, the lens follows the same pattern of sharpness - very good at ƒ/2.8, excellent at ƒ/4 to ƒ/8, and softer at ƒ/16 and ƒ/22. In this case however we note softer corners than seen on the GX-1, owing to the larger sensor being viewed by the lens.

Chromatic Aberration
Chromatic aberration is notable with the lens attached to both camera bodies: on both bodies, it's viewed in the corners, in areas of high contrast. In images shot with the Panasonic GX-1, it appears as magenta-green fringing, and in images shot with the Sony NEX-7, it appears as magenta fringing. It gets marginally better with either camera if you stop down, but only slightly.

Shading (''Vignetting'')
With the Sigma 19mm ƒ/2.8 mounted on the Panasonic GX-1, corner shading isn't really an issue. However when the lens is mounted on the Sony NEX-7, there is always at least a slight amount of corner shading: at ƒ/2.8, the corners are almost a half-stop darker than the center; stopped down, the corners are 1/3 EV darker than the center.

Distortion
Results for distortion testing with the Sigma 19mm ƒ/2.8 DN are the same with both cameras: there is some notable barrel distortion in the corners of the images (around +0.5%).

Autofocus Operation
The Sigma 19mm ƒ/2.8 DN uses an in-lens motor for focus and is very fast to do so: focusing from infinity to close-focus took well less than one second. There is no extension of the lens during focus operations and attached filters will not rotate.

Macro
This is not a lens with any significant macro capability: it only offers 0.14x magnification, with a minimum close-focusing distance of just under 8 inches (20cm).

Build Quality and Handling
The Sigma 19mm ƒ/2.8 EX DN is a fairly pedestrian lens, small and light with a matte black finish. The lens is made of primarily plastic components, weighing only 140 grams (4.9oz), with plastic 46mm filter threads and a metal lens mount. The lens has only one control on it, the manual focus ring. There is no depth-of-field scale, distance scale or infrared index.

The focusing ring is about 3/4'' wide, with deep, easy-to-grip plastic ribs. There are no stops, hard or otherwise, at the close-focusing and infinity end of the lens.

The included lens hood is plastic, attaches via a bayonet mount, and can be reversed onto the lens for storage. The interior of the hood is ribbed, and when attached to the lens it adds about 3/4'' to the overall length.

Alternatives

Sony E 16mm ƒ/2.8 SEL16F28 ~$250
For the Sony users, the Sigma 19mm ƒ/2.8 offers a slightly longer alternative to the Sony 16mm ƒ/2.8. In this case however the Sigma also offers a sharper alternative, with the 19mm ƒ/2.8 offering significantly sharper results throughout the same apertures. Other test results are also better: CA is better handled, there is slightly less corner shading, and distortion is a bit less severe (naturally barrel-distorted rather than pincushion).

Panasonic 20mm ƒ/1.7 ASPH LUMIX G ~$400
At almost double the price of the Sigma 19mm, the Panasonic 20mm offers slightly sharper results with less CA. There is somewhat significant corner shading, but almost zero distortion.

Olympus 17mm ƒ/2.8 M.Zuiko Digital ~$300
Olympus offers a wider alternative to the Sigma, which is about on the same level optically: however, we would give a nod to the Sigma for its better tolerance to chromatic aberration, and slightly sharper performance. In this case, the Olympus makes for a slightly smaller.

Conclusion
There are a surprising number of alternatives in this category - wide primes for mirrorless cameras - so Sigma's offering comes at an interesting time. It holds its own in our tests, providing a sharp image even wide open at ƒ/2.8, with only slightly notable chromatic aberration in the corners. It's not a case of Sigma finding a niche other manufacturers haven't exploited, however, Sigma does undercut all the current manufacturers with a lower price point. If you haven't got a wide angle prime for your micro four-thirds mirrorless camera, or your Sony NEX camera, then you may want to consider the Sigma 19mm ƒ/2.8 DN.

Product Photos

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.