Sigma 19/2.8 DN and Sigma 30/2.8 DN for Micro four-thirds Review
These lenses replace the earlier 19mm f2.8 EX DN and 30mm f2.8 EX DN which have now been discontinued. The 19mm f2.8 DN | A uses three molded aspheric elements and is a telecentric design. The new 30 f2.8 DN | A is also a telecentric design and uses two aspheric elements with three aspheric surfaces. My understanding is that these new lenses use the same optical design as their predecessors. The differences are cosmetic and the fact that the new DN series lenses go though a new testing procedure using, in Sigma’s words “…our own A1* proprietary MTF (modulation transfer function) measuring system using 46-megapixel Foveon direct image sensors. Applying this system, we check each lens in our new lines at our Aizu factory, our sole production site. Even previously undetectable high-frequency details are now within the scope of our quality control inspections, allowing us to deliver consistently high lens performance…”
Both these lenses are in Sigma’s new “ART” category and have a shiny chrome circle with an “A” in the center on them. From what I can tell, Sigma give this “A” designation to lenses which “…are developed with an emphasis on artistic touch and are designed to meet the expectations of users who value a creative, dramatic outcome…this category will be comprised of many focal lengths and designs, such as large-aperture prime lenses, wide-angle lenses, ultra wide-angle lenses, and macro and fisheye lenses…”
Externally the two lenses are very similar with a “stealth” styling. Looked at from the front at first there seems to be no visible marking around the lens, but on closer inspection you can see that the lens identification is in fact molded into the rim around the lens perimeter, but it’s black on black, so you have to angle the lens to the light to see it. This monochrome theme is also applied to the lens which is a single color and almost a single texture. Instead of a rubberized focus ring as is found on most lenses, the focus ring is smooth metal with no markings. It does have a slightly shinier finish than the static part of the lens barrel, which has more conventional data printed on it in white (printing on the silver version is in black). There is no focus distance scale, no DOF scale and the focus ring will spin continuously since even manual focus is electronic rather than mechanical (“focus by wire”) .
While not large and certainly smaller than similar focal length lenses deigned for conventional DSLRs, neither is particularly small for a micro-four thirds lens. Slightly surprisingly, the 19mm is larger than the 30mm. They are not “pancake” designs.
The AF motor used in these two lenses is a linear motor which is very quiet. When no power is applied to the lens, the inner focusing elements appear free to move, so if you shake the lens back and forth there’s a “clunking” noise. This is normal, so if your lens “clunks” when moved it’s not a problem. The almost silent operation enables AF during video recording with minimal disturbance to the soundtrack.
Focus is internal, so no external part of the lens extends or rotates during focusing. The maximum magnification of the 30mm f2.8 DN | A is 0.123x while the maximum magnification of the 19mm f2.8 DN | A is 0.135×. Both lenses accept 46mm filters.
Since the digital multiplier for four-thirds sensors is 2x, the 19mm f2.8 DN will have a similar field of view to a 38mm lens on full frame 35mm, which means it’s a semi-wideangle lens. Similarly the 30mm f2.8 DN has a field of view on four-thirds similar to that of a 60mm lens on full frame 35mm, which means it’s a normal-short telephoto.
Both lenses are supplied with a hood and a small, zippered, padded carrying case. The case does not have provision for attaching it to a strap or belt.
Sigma 30 mm f2.8 DN | A Sigma 19 mm f2.8 DN | A Focal Length 30 mm 19 mm Aperture Maximum: f/2.8, Minimum: f/22 Maximum: f/2.8, Minimum: f/22 Camera Mount Type Micro Four Thirds Micro Four Thirds Angle of View 39.6° 59.3° Minimum Focus Distance 11.8" (29.97 cm) 7.9" (20.07 cm) Maximum Reproduction Ratio 1:8.1 1:7.4 Groups/Elements 5/7 6/8 Diaphragm Blades 7 7 Filter Thread Front: 46 mm Front: 46 mm Dimensions (DxL) Approx. 2.39 × 1.59" (60.8 × 40.5 mm) Approx. 2.39 × 1.80" (60.8 × 45.7 mm)
There’s really not much to handle! The lenses mount on the camera as you would expect and there are no external switches on them. Switching between manual and autofocus is done by the camera body, not the lens. The lenses are not optically stabilized since most four-thirds cameras (e.g. the Olympus PEN series) employ stabilization via a sensor shift mechanism in the camera.
Autofocus is fast, accurate and essentially silent. Manual focus is a longer story. When the camera is switched to manual focus mode you can control focus using the smooth metal ring at the front of the lens barrel. My E-PL1 is setup so that as soon as the manual focus ring is turned in MF mode, the LCD display magnification is increased to assist in focusing. The E-PL1 can be setup so that the direction in which the focusing ring has to be turned to move from infinity to close focus can be set to either clockwise or anticlockwise.
Manual focus is smooth but with a catch. The catch is that if you grip the focusing ring too tightly, it sticks. OK, so don’t grip it tightly…but Olympus chose to make it smooth and shiny rather than textured and rubbery so that you tend to to grip it tightly to get a good feel as to whether you are actually rotating it or if your fingers are just slipping on the smooth surface. You can, with some thought, grip it “just right”, so that it doesn’t stick and your fingers don’t slip. You eventually get used to this, but I can’t help but think that a nice ribbed rubberized finish would have been more user friendly. The same issue was found on both the 19mm and 30mm lenses. Maybe a thicker, stiffer focusing ring or greater gap would cure this problem if Sigma really wanted to stay with the smooth shiny focusing ring for aesthetic reasons.
There’s good and not quite so good here. The good is that Sigma supply a lens hood with each lens rather than making you go out and buy one as an accessory. The not quite so good is the fact that that both lenses are supplied with the same hood (LH520-03 ), and it’s the same hood as is supplied with the APS-C NEX versions which have a wider field of view due to the smaller crop factor there. The result is that the hoods do not provide optimal shading of the lens. They are quite a bit wider than they need to be. For example the 30mm lens on a micro four-thirds camera has a FOV of 39.6 degrees, The 19mm lens on an APS-C camera has a FOV of 73.5 degrees. Clearly a lens hood designed for the wider lens isn’t going to be optimum on the narrower lens, so both the 59.3 degree 19mm and the 39.6 degree 30mm get a hood that’s probably designed for an angle of view of at least 75-80 degrees.
Though Sigma describe both lenses as “fast” and “large aperture” and talk about the quality of out of focus backgrounds, f2.8 isn’t really very fast and backgrounds might not blur as much as you might think, especially with a four-thirds sensor camera since smaller sensors generally give rise to larger DOF for a given lens coverage and aperture.
Backgrounds do blur a lot more than they would with a fixed lens compact digicam though, since they use much smaller sensors. Just don’t expect the extreme background blur effects that you can see with longer, faster lenses on full frame 35mm.
When mounted on the camera and with the camera turned on, the lenses stop down as the light gets brighter, giving rise to a “chattering” sound as the light varies. Other micro four-thirds lenses also do this, but the noise from the 30/2.8 and 19/2.8 was quite a bit more noticeable than from my other micro-four thirds lenses (an Olympus 14-42/3.5-5.6 and a Panasonic Lumix 45-200/4-5.6).
Both the 19/2.8 and 30/2.8 lenses use a rounded 7 blade aperture and cover the range from f2.8 to f22.
Close Focus Magnification
The specification of the lenses give a maximum magnification of 0.123x for the 30mm f2.8 and 0.135xfor the 19mm/2.8. These numbers may sound a little low to those used to full frame 35mm lenses, but since the four-thirds sensor is only 1/2 the size of a full frame sensor, the linear field of view is 1/2 that of full frame 35mm lenses with the same magnification.
I measured the linear field of view at closest focus to be approximately 3.9″ × 2.9″ for the 19mm lens and 4.8″ × 3.6″ for the 30mm lens. Not by any means “macro”, but enough for frame filling shots of larger flowers.
In the center of the field, both the 30/2.9 and 19/2.8 are very sharp. In fact little if any increase in sharpness can be seen when they are stopped down to f4 or f5.6. If center sharpness is your main priority then you should have no hesitation in using these lenses wide open.
Wide open at f2.8, the corners of the 30/2.8 and 19/28 image are still pretty good, though not up to the same level of sharpness as the center. Stopping down does bring up the corner sharpness and shooting RAW (see below) also helps, but unless you’re going to be making large prints or viewing the images at 100% on a monitor there’s no great need to stop down for increased sharpness.
Chromatic aberration appears to be well controlled in both lenses when looking at JPEGs straight out of the camera. On high contrast features near the edges and corners of the frame viewed at 100% slight color fringing can be seen. However the level of chromatic aberration is low enough that again it’s not something you would notice unless making large prints or viewing at over 100% on a monitor.
However, looking at the RAW (.ORF) files it’s evident that the camera I was using (Olympus PEN EPL-1) was applying some chromatic aberration correction to the images. The RAW files showed a little higher level of CA with more intense colors. Tweaking the RAW file (I used RawTherapee), CA could be essentially eliminated, yielding imaged better than the JPEGs from the camera and with essentially zero CA. The image on the right shows the CA in an uncorrected shot taken with the 19/2.8 at f6.3. It also shows the excellent sharpness with edge sharpness approaching that of the center after correction has been applied.
Distortion is low. Both lenses show a small amount of barrel distortion. For the 30mm I measured around 0.5%, but it’s a little higher for the 19mm, measuring around 1%. In neither case is it likely to be noticeable in most images and if it is, digital correction of distortion is normally quite effective.
Vignetting is pretty well controlled in both lenses. For the 30/2.8 there’s about 1 stop of vignetting in the corners wide open, dropping to about 1/2 stop at f5.6. It’s slightly higher with the 19/2,8 at around 1.3 stops wide open and 2/3 stop at f5.6
Out of focus backgrounds seem generally smooth (good bokeh), though these are short focal length moderate speed lenses and so their ability to throw backgrounds out of focus is somewhat limited. The 30/2.8 is better in this regard then the 19/2.8 as would be expected.
Since I have a relatively ancient Olympus PEN E-PL1 it’s probably not fair to judge the AF tracking performance of the lenses on the basis of hardware that’s not current. AF tracking did work OK with a little focus hunting at times.
The linear AF motor is very quiet. So quiet that you can’t really hear it at all, but on the audio track of recorded video there were some fairly quiet “ticks” or “pops” which appear to be the result of the linear AF motor changing position to keep the image in focus. There’s certainly no “whirring” of a conventional motor. Focus tracking seemed better with the new Sigma lenses than my old Olympus 14-42 zoom and the recorded noise of the focusing motor was much lower
Optically both the
Olympus Pen E-PL1 with Sigma 19/2.8 DN @ f8
On the downside the potentially sticky smooth and shiny focusing rings seem to be more of a nod to design than utility, though once you get used to not gripping them too tightly they’re OK. The chattering aperture noise and stopped down viewing in bright light is something to get used to, but presents no real problem and other micro four-thirds lenses do it too.The hoods are nice to have as standard, but aren’t optimized for the lens’ field of view. Still, any hood is better than no hood so kudos to Sigma for supplying one with the lens.
While I think that many micro-four thirds fans would have been more excited by lenses that were smaller (pancake designs) or faster (f2 or f1.4), no doubt such lenses would have been significantly more expensive. The Sigma 19/2.8 and 30/2.8, while they may not be super exciting in terms of focal length or speed, are nevertheless very good lenses and well worthy of consideration if you’re looking to step up from a slower zoom kit lens.
If you are one of the four-thirds fans looking for something a little more exotic in this general focal length range, Sigma used to have a 30mm f1.4 EX DC HSM in the Four-Thirds mount, but they upgraded it to the 30mm f1.4 DC HSM | A and for some reason don’t offer the new version in a micro four-thirds mount. There’s is a