The Sigma 30mm f/2.8 DN is Sigma’s first entry in to the mirrorless lens market. The lens comes in both NEX and m4/3 lens mounts, which is unfortunately only in that the lens would probably be at least slightly smaller if it had been designed for m4/3 only. The lens has an odd 30mm focal length, but for NEX cameras it is a more normal 45mm equivalent instead of the 60mm equivelent on m4/3 cameras. I’ve found however that it slots nicely between 45mm and 20mm focal lengths…though as it stands I don’t, as of this writing, HAVE a 20mm focal length lens. My ideal setup is a 14, 20, 30 and 45mm lenses though as it gives about a 50% jump in field of view for each lens.
The lens elements are extremely small for the lens, but it is also a very modest f/2.8 maximum aperture. The lens is extremely light despite the size though. The lens takes 46mm filters like a number of other m4/3 primes. The lens barrel is 60.6mm in diameter and 38.6mm in length (which is huge compared to a bunch of the pancakes out there right now for m4/3). The lens is a svelte 135g however due to mostly plastic construction with a metal bayonet mount. The lens is composed of 7 elements in 5 groups with 2 of the elements being aspherical. The lens has a new type of linear AF motor that moves an internal lens element/group for focusing (no front rotation or extension on focusing). It is apparently some type of linear motor and when the lens is off the focusing element is lose so it’ll rattle back and forth a bit. The autofocus of the lens is extremely fast and silent however. One issue, at least on Olympus m4/3 bodies is that it delays camera startup time. On the E-PL1 and E-M5 normal startup is maybe .8-1s, but with the Sigma 30mm mounted it is around 3-4s, which can be rather annoying. The lens has a minimum focusing distance of .3m leading to a reproduction size of about 8.1:1.
A big selling point of the lens is that it is extremely cheap as well as, to a degree, the focal length. The lens runs $199 brand new out the door most places in the US and includes a lens case and caps. The overall optical quality is pretty good. There is a bit of chromatic aberration, but in general it isn’t severe. The lens in the center is very, very sharp from wide open and in the corners it is a little soft wide open and sharpens up some upon stopping down (as you can see from the map test further on in this review). Distortion is extremely low and vignetting wide open is slight and disappears completely upon stopping down. Back to the price for a minute, at least if you are going to reach for primes, the current normal or near normal focal length range really only has 3 or 4 options right now depending on your point of view. There is the Panasonic Leica 25mm f/1.4, which runs upwards of $550 new. You have the Panasonic 20mm f/1.7 which runs from $340 upwards of $400 because of its general scarcity (the 25/1.4 is also generally scarce). Then you have the Sigma 30mm f/2.8 a little longer than standard and the Sigma 19mm f/2.8 at a little wider than standard as well, but of which run $199 and are very easy to get and in general have good, if not outstanding optical quality.
Here are the map test images for the lens. The tests (from top to bottom) are f/2.8, 4, 5.6 and 8. The left are the center tests and the right the extreme top right corner. As you can see the center is very sharp from wide open. The corners to me to have some vertical smearing that makes it appear soft wide open. At f/4 things improve and at f/5.6 they are what I would consider sharp. Things improve a little more at f/8.
Here are a couple of full resolution images. From processed OM-D E-M5 processed RAW in lightroom 4.1, really only a touch of CA removal on the picture of the kids. Otherwise nothing other than standard camera profile.
- Very low price ($199 US new)
- Very fast and silent focusing
- Great center resolution, even wide open
- Very light lens
- Low vignetting and distortion
- Extreme corner resolution is a little weak wide open and never gets really sharp on stopping down
- Slow camera startup times (at least with Olympus m4/3 cameras as of this writting)
- Modest maximum aperature of f/2.8
- Relatively large size for its focal length and aperature size