Sigma 30mm f/2.8 EX DN

SLRgear Review
March 26, 2012
by Andrew Alexander

Sigma announced the availability of its made-for-mirrorless DN (''Digital Neo'') lenses earlier in 2012, with the 30mm f/2.8 DN and the 19mm f/2.8 DN. Both lenses are made for the micro four-thirds mount and the Sony NEX E-mount. For micro four-thirds cameras such as the Panasonic G3, on which we tested the 30mm ƒ/2.8 DN, the lens provides an equivalent field of view of 60mm; on the Sony NEX camera the lens provides an equivalent field of view of 45mm.

The lens takes 46mm filters, but from our limited research there does not appear to be a matching lens hood. The lens is available now for approximately $200.

Sharpness
The Sigma 30mm ƒ/2.8 is very sharp indeed, even when used wide open at ƒ/2.8. It's not tack-sharp corner-to-corner at that aperture, but it offers a large area of central sharpness with only light corner softness. There are marginal improvements to both corner and central sharpness at ƒ/4 and ƒ/5.6, where it achieves maximal sharpness. Sharpness actually drops off slightly at ƒ/8 and smaller, but there's no noticeable impact until ƒ/11. The lens can stop down as small as ƒ/22, where overall image sharpness is somewhat degraded.

Chromatic Aberration
There is some fairly significant chromatic aberration present in images shot with the 30mm ƒ/2.8. It's visible as fringing in areas of high contrast, showing up as magenta-blue fringing. It's more or less consistent regardless of the aperture selected.

Shading (''Vignetting'')
Light falloff really isn't in an issue with this lens, with the worst effect showing corners that are just over 1/4 EV darker than the center, at ƒ/2.8.

Distortion
There's fairly little distortion to speak of with this lens - just a slight amount of barrel distortion in the corners (+0.25%).

Autofocus Operation
The 30mm ƒ/2.8 uses an in-lens motor for autofocus, which is quick and quiet, taking just under a second to go from infinity to close-focus. The front element does not rotate during focusing operations, making life that little bit easier for polarizer users.

Macro
Offering 0.12x magnification, the 30mm ƒ/2.8 offers poor macro performance, with a minimum focusing distance of just 30cm (around a foot).

Build Quality and Handling
The Sigma 30mm 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 128 grams (4.8oz), 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. It's worth noting that the focusing lens elements that move are loose inside the lens when not attached to the camera so they make a rattling noise: Once attached to the camera the linear focusing motor is engaged and there is no more noise.

Alternatives

Sony E 24mm ƒ/1.8 Carl Zeiss Sonnar T* ~$1,000
As an E-mount alternative, the price differential is justified: in addition to being as-sharp as the Sigma 30mm ƒ/2.8, the Sony E 24mm deals better with chromatic aberration and offers a much wider maximum aperture of ƒ/1.8.

Sony E 30mm f/3.5 Macro ~$300
Also for the E-mount, Sony's 30mm ƒ/3.5 doesn't offer quite as sharp an image in the corners, but then, we're not looking at an apples-to-apples comparison: our test of the Sigma 30mm f/2.8 was done on the micro four-thirds Panasonic G3, so the true corner performance of the Sigma may indeed be poorer than presented. Obviously the macro performance of the Sony is much greater than the Sigma, as well as slightly better performance for CA and distortion, at the cost of a slightly smaller maximum aperture (ƒ/3.5 instead of ƒ/2.8).

Olympus 25mm f/2.8 Zuiko Digital ~$250
For the micro four-thirds mount, the tiny Olympus 25mm pancake is certainly the winner when it comes to lightness, also providing excellently sharp images. CA is treated well, except when the lens is stopped down significantly, and distortion is slightly higher than the Sigma.

Panasonic 25mm f/1.4 ASPH Leica DG SUMMILUX ~$600
Panasonic's option for the micro four-thirds mount in a similar focal length range is a bit more expensive, but offers the fastest aperture setting of them all, a full two stops faster at ƒ/1.4. Even wide open at this aperture the lens is exceptionally sharp (sharper than the Sigma, except in the corners), and distortion is surprisingly non-existent. CA is somewhat prominent in the corners but overall, well-controlled.

Conclusion
You have to hand it to Sigma, they recognize the opportunity in creating lenses for multiple brands, and have found yet another niche to supply lens alternatives in the micro four-thirds and NEX camps. The Sigma 30mm ƒ/2.8 EX DN provides an excellent alternative for not a lot of money: optically, it's very good, at least as good as the alternatives in its price range.

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.