Introduction

Sigma 30mmf/1.4 EX DC HSM is currently the only non fish-eye fixed focal lens in Sigma's arsenal that was designed from grounds up for APS-C type cameras. The lens has a reduced imaging circle and while it can in theory be mounted on a full-frame of APS-H type cameras, the lens will vignette severely, making it unsuitable for most scenarios. The company currently offers the lens in Canon, Nikon, Sigma, Pentax, Sony/Minolta as well as Four Thirds mounts. The lens is priced quite aggressively, with new samples going for ~US$380 (as of November 2007).

The optical construction of the lens consists of 7 elements in 7 groups, including two SLD (Super Low Dispersion) glass elements and a single aspherical glass element designed to reduce various forms of aberration. THe build quality is pretty good and similar to other EX type finish, Sigma 30mm f/1.4 EX DC HSM features a hard plastic barrel with fully rubberized focus ring and metal mount. The lens offers HSM-type AF along with full-time manual focusing system, controlled by an AF/MF switch on the side of the barrel. The lens is pretty light and compact, weighing 430g (15.2oz) and measuring 75 x 59mm (2.9 x 2.3in) and since the lens sports a true inner focusing design, the overall length of the barrel remains constant throughout the focusing range.

Like most modern lenses, 30mm EX DC HSM sports a fully electronic aperture control, meaning there's no dedicated manual aperture control ring and all aperture settings have to be set directly from the camera. The minimum focusing distance is 40cm (15.7in), the minimum supported aperture is f/16 and the lens accepts 62mm screw-in type filters.

Image

As mentioned earlier, the lens is designed for APS-C type cameras and on a full-frame body the field of view of the lens will be similar to that of a 48mm lens, which makes it a standard, rather then a wide angle lens. The factory box includes Sigma 30mm f/2.8 EX DC HSM lens, front and rear caps, Dia-Petal shaped lens hood, soft vinyl case, manual and registration card.

 

Summary
Lens Composition 7 elements in 7 groups
Angular Field 45 degrees
Minimum Focus 40cm/15.7in
Focusing Action AF/MF
f-stop Scale f/1.8-f/16, camera-controlled
Filter Size 62mm
Lens Hood Dia-Petal (included)
Weight 430g/15.2oz
Dimensions 75.7x59mm/2.9x2.3"
Lens Case Vinyl (included)

 

Field Tests

The lens did not fare exceptionally well in the field, showcasing very decent center quality, but suffering around borders. Visually, border quality was noticeably softer, especially at wider apertures, where images looked bleak and lacked contrast. While it is pretty common trend for wide angle lenses to have softer borders at wide aperture levels, it is also expected that the image quality will improve with stopped down apertures - Sigma 30mm f/1.4 EX DC HSM did not seem to back this trend and borders remained noticeably soft even at f/2.8 and f/4.

 

Vignetting @ f/1.4 - 1.6x crop
Vignetting @ f/1.4 - 1.6x crop

 

Surprisingly for a wide angle lens with such a fast maximum aperture, Sigma 30mm f/1.4 EX DC HSM showed quite low level of vignetting. Granted the lens takes advantage of a smaller APS-C image sensor, nevertheless, this is quite a positive surprise. The lens did produce some color fringing pretty much across the frame and minor levels of flare with wide open aperture as well as minor barrel distortion.

 

ISO 100, f/1.4, 1/4000, 30mm
ISO 100, f/1.4, 1/4000, 30mm

 

Lab Tests

Please note that MTF50 results for APS-C and Full-Frame cameras as well as cameras from different manufacturers are not cross-comparable despite the same normalized [0:1] range used to report results for all types of cameras.

 

Canon APS-C: The lens showed somewhat mixed results in the lab. Center performance was outstanding almost throughout the entire aperture range. I say almost because at f/1.4 the lens struggled a little bit, producing average (but not disastrous) results. Border quality is a completely different story here though. Here the lens does not show any special characteristics and image quality is pretty dismal. Performance slowly improves with stopped down aperture, but does not reach decent levels until f/8, which is quite disappointing. At its peak, the lens would be capable of producing outstanding 16in prints, which is not quite what one would expect from a fixed focal lens. Conclusion? Not the performance king, but not the worst either. Center quality is quite good but then again, most lenses these days are capable of producing excellent center quality.

 

MTF50 (Line Width/Inch on the Print) @ 30mm
MTF50 (Line Width/Inch on the Print) @ 30mm

 

Normalized raw MTF50 @ 50mm
Normalized raw MTF50 @ 50mm

 

Chromatic aberration was quite low in the center, not exceeding ~0.2px throughout the aperture range, however CA creeps up around borders, where it averages ~1.1px with wide open aperture and ~0.9px from f/2 through the rest of the tested aperture.

 

 

Image borders @ 30mm (100% crop): f/1.4 vs f/8
Image borders @ 30mm (100% crop): f/1.4 vs f/8

 

Alternatives

There are quite a few wide angle lenses available on the market these days, but very few of those are specifically designed for APS-C type cameras. So to find the best lens, expand your search to FF lenses. Take a look at Canon's EF 24mm f/1.4L USM (review), which offers pretty good image quality from f/2.8, but is rather pricey. So is Canon EF 35mm f/1.4L USM (review). Within Sigma's ultra wide lens lineup, 20mm f/1.8 EX DG ASPH HSM  (review) offers a decent image quality with stopped down apertures.

 

Recommendation

Sigma 30mm f/1.4 EX DC HSM is currently the only wide angle prime that was specifically designed for APS-C sensors and as such it has no direct competition. Nevertheless, users should carefully review the benefits this lens provides versus the more traditional FF type wide angles. On the positive side we have pretty decent center image performance, low levels of vignetting, good build quality along with affordable price. On the negative side, we have poor border performance, occasional flare and color fringing. Are these limitations acceptable? Maybe, assuming you cannot find a better alternative.