Wednesday, 20 February 2013

Sigma 19mm f/2.8 EX DN review

The Sigma 19mm f/2.8 EX DN was released at the same time as the Sigma 30mm f/2.8 EX DN. Together, these were the first Sigma lenses designed specifically for mirrorless camera systems, and were released for the Sony E-mount and Micro Four Thirds mount in 2012.

Both of these lenses have somewhat odd focal length for the Micro Four Thirds format, compared with conventional prime lenses. The 19mm lens has the same field of view as a 38mm lens on a traditional film camera, while the 30mm lens corresponds to 60mm. Both of these focal length equivalents are unusual.

However, the answer to these odd focal lengths lie in the fact that the lenses were designed for the APS-C format. With a smaller crop factor of 1.5x, the lenses correspond to the 28mm and 45mm, i.e., the classic wide angle and normal lens, respectively.

Also, keep in mind that while 19mm is an odd focal length for Micro Four Thirds, it is very close to 20mm, and the Lumix G 20mm f/1.7 is a very successful lens. They are both shown below:





Physical appearance

First of all, please note that the lens has changed appearance. What you see here is the first revision of the lens, which has an outer plastic shell, and ribbed plastic focus ring. In 2013, the lens received a cosmetic facelift, with a metal shell, and a smooth metal focus ring. Otherwise, the old and the new lenses are the same. So you can still use the optical tests here when considering the new version of the lens.

Just like its sister lens the Sigma 30mm, this lens rattles. Something is loose inside the lens when it is not in use. This is a bit annoying, but no problem. Once the lens is connected to a camera, and the camera is turned on, the rattling stops.



Again, just like the Sigma 30mm, the rear lens element is recessed quite far into the lens mount:



Since the register distance of the Micro Four Thirds format (20mm) is fairly close to that of the Sony E-mount (18mm), this does not seem to be the explanation for the very recessed rear element. I'm guessing the explanation is that the lens was designed to be used also on the Samsung NX mount, which has a significantly longer register distance of 25.5mm. At this time Sigma has not released the lenses for Samsung NX, but perhaps they will in the future if the format takes off.

The exterior of the lens is black matte plastic, and it has a quite non-obtrusive look.

The focus ring is wide, and made out of ribbed plastic. It rotates smoothly, with a reasonable amount of dampening. The focus is of course "by wire", just like virtually all the other Micro Four Thirds lenses. There is no mechanical connection between the focus ring and the actual focus distance of the lens. And there is no focus scale.

Autofocus


There is a small start-up delay when powering on the camera, unlike most other lenses. The delay is around 1.5 seconds, shorter than for the Sigma 30mm lens.

The autofocus is fast and virtually inaudible. Here is an autofocus speed comparison with the Lumix 20mm f/1.7 pancake lens. As expected, the 19mm lens focuses much faster. There is also a big difference when using the lenses for video. Here is a side by side comparison with the 20mm lens, which shows much better performance when using the 19mm lens. Both lenses are set to f/2.8:



While the autofocus speed is not quite as fast as the modern zoom lenses, it is still more than fast enough, and should be no problem at all for normal use.

Sharpness


I made a sharpness comparison with the Lumix G 20mm lens. It shows that the 20mm lens is the best, no doubt about it. But the Sigma 19mm lens is still quite good.

Here is another sharpness test, compared with the Lumix X 12-35mm f/2.8. The full images at f/2.8 are here:






In terms of sharpness, the two lenses are fairly equal in the centre. However, in the corner, they are far apart. Here are 100% crops from the top left corner:



We see a quite clear difference. The Sigma 19mm lens suffers from some Chromatic Aberration artefacts (red and green fringing). While the colour fringing can be corrected in an image processing program, there is also some more general dullness. When stopping down, the performance improves some.

Geometric distortion


The Lumix G 20mm f/1.7 lens relies on in-camera geometric distortion correction. The Sigma 19mm f/2.8 does not. However, the output image is not 100% rectilinear, as you can see below.



This is not that unusual. In fact, the Lumix 20mm lens, even after the in-camera adjustment, features some residual barrel distortion. And when photographing people or nature, this is no issue at all, nobody will notice the barrel distortion. But if you use this lens to photograph cityscapes and architecture, you will surely find this problematic.

Bokeh


I compared the bokeh of the 19mm lens with that of the 20mm and 12-35mm lenses here. The 19mm lens has more pleasing bokeh than that of the Lumix G 20mm f/1.7.

Compared with the Sigma 30mm f/2.8


In my opinion, the Sigma 30mm f/2.8 EX DN lens is quite good considering the price. The 19mm lens does not shine quite as much, with more CA artefacts in the corners, and a lower level of sharpness. They both have nice bokeh and fast focus, though.

Compared with the Lumix G 20mm f/1.7


Make no mistake about it, the Lumix G 20mm f/1.7 is a better lens. It is sharper, faster (in terms of aperture), and much more compact. In terms of bokeh, though, I think the 19mm lens is better. The 19mm lens also focuses much faster, and less audibly. For video, I would use the 19mm lens, unless I really need the extra aperture, and can do without autofocus.


Lens

Lumix G 20mm f/1.7

Sigma 19mm f/2.8
Focal length
20mm
19mm
Aperture blades
7
7
Aperture rangef/1.7-16f/2.8-22
Lens elements/groups7/58/6
Front lens thread46mm46mm
Diameter62mm61mm
Length26mm46mm
Weight100g140g
Minimum focus0.2m0.2m



You may consider to buy the Sigma 19mm lens over the Lumix 20mm lens to save money, as there is a significant price difference. Or if you need a better autofocus performance during video. But for the best optical performance, the Lumix G 20mm f/1.7 is the better choice.

New version of the lens


This lens is in fact already discontinued. Replacing it is a new version of the lens, called Sigma 19mm F2.8 DN, and is part of Sigma's "Art" line of lenses. It has the same optical design, but a different exterior. The focus ring is now made out of smooth metal. The lens is available in silver metal finish, and in black finish:



From an ergonomic point of view, this is a strange choice. A smooth surface appears to be poor material for a focus ring. On the other hand, handling it feels surprisingly good. So I would say that this is no real issue. It looks like the remake is all about a new styling, and not any change to the optical properties.

Example images


Here is an example image to illustrate the out of focus rendering at close focus image, at full open, f/2.8. The focus was set to the rose in the lower left corner:



The bokeh is generally very nice, however, there is a bit of ringing in the top right corner.

Another example image, with a focus distance of about 3 meters, at f/3.2, 1/60s:



And here are some 100% crops, which illustrate the CA artefacts in the top left corner, and that the quality is good in the centre:



Conclusion


While the Sigma 30mm f/2.8 gave a good value for money in terms of optical performance, the Sigma 19mm f/2.8 can be seen as more lacking. And with the Lumix G 20mm f/1.7 outperforming the Sigma 19mm, it is hard to recommend the Sigma lens, unless you are on a tight budget, or if autofocus performance during video is important to you. The Sigma 19mm lens is not bad, far from it, it just doesn't reach up to the Lumix G 20mm lens, or the sister lens, the Sigma 30mm f/2.8.

18 comments:

  1. Like the Panasonic 20mm I've had this Sigma 19mm clearly exhibit some moire using it on my GH1. A recent example of this suggests to me the lens is very sharp. Is it also out resolving my GH1's 12mp sensor?

    ReplyDelete
    Replies
    1. I don't know. Are you getting moire during video? Or do you talk about still photography?

      Delete
    2. Only stills. Video has always seemed moire free with the GH1.

      Delete
    3. Ok. I'm not sure what to make of this.

      Moire probably means that the lens is quite sharp. Which is good.

      Further, when you're getting moire, it is usually a sensor issue, not a lens issue. It could mean that the sensor has too weak AA filter.

      Delete
  2. If you don't recommend this lens, and the 20mm 1.7 is a bit pricey, what other option do you suggest???

    ReplyDelete
    Replies
    1. The lens is recommended if you're on a budget. So if the Lumix G 20mm f/1.7 lens is too expensive, the Sigma 19mm f/2.8 can be an alternative. But the 20mm lens is clearly better.

      Delete
  3. I have read that the GH1 had a very weak AA filter and perhaps this is evidence. I'd much rather have the sharp images the camera gives me than not and now that LR has the excellent moire reducing tool it is even less a problem.

    ReplyDelete
    Replies
    1. Some like cameras with weaker AA filters, as they can theoretically give a higher resolution. On the other side, a weak AA filter can more easily give moire and other negative side effects, that may be difficult to fix in post processing. So it is a bit of a balance.

      Delete
  4. 6 months ago I tested this lens and returned it due to the slow startup time and worrisome rattling you mention.
    At CES this January I tested the lens again because I was assured by the Sigma staff that this was the identically-looking "second generation" of the lens. Startup time was about 0.2 seconds. Rattling was almost un-audible, more like faint clunking. It was explained to be because of the auto-focus mechanism which was said to be "of a similar type as used in optical stabilization, not the usual electromagnetic motor".

    You seem to have a "Gen 1" copy, whatever this may exactly mean.

    ReplyDelete
    Replies
    1. Was the lens you tested the new version with the smooth metal surface? If so, it appears that the new lens also has changes to the focus mechanism, beyond the cosmetic change.

      Delete
  5. As I mentioned, the lens I tested at CES looked identical to the lens I bought, tested and returned 6 months ago.That was the very same lens subject of your review.

    The new smooth surface lens was not available at CES.

    ReplyDelete
  6. To the original Anonymous, I think the Sigma staff was telling some truth.

    My 19mm (which was bought last month with a 30mm as a kit)does not have any significant start up lag. I'd say mine takes slightly less than 1 second before I can see the live view screen and focus. Some owners (who also bought the kit from the recent batch) also comments on forums that they don;t notice any long start up lags. It baffles me why some reviewers claim a lag of 3-4 seconds.

    The original Anonymous comment made sense and I really think Sigma have revised the autofocus mechanism. I also noticed my 19mm is sharper than my 30mm which match the results of another reviewer (I won't mention the website but he tested mutiple copies of the 19mm and 30mm, with the 19mm on average producing higher resolution than the 30mm).

    ReplyDelete
    Replies
    1. My 30mm lens has a long startup lag. You can see it documented in this video. It's good that Sigma has addressed this, on the other hand, it is not much of an issue.

      Delete
  7. Thank you for a wonderful blog!
    I have a question concerning the Sigma 19mm lens discussed in this post.
    I notice in your video AF comparison that the Sigma 19mm lens produces fast "jittering" at times when it focuses (on AF). I saw another video of the Sigma MFT lens, and similar jittering happened while autofocusing during video shoot.
    The AF on the Sigma looks wonderfully fast but the jitter looks disturbing, and the comparison Panasonic 20mm does not jitter. Have you noticed whether this is a constant side-effect of video AF with this Sigma 19mm lens?

    ReplyDelete
    Replies
    1. I think what you are seeing is the "focus breathing". Read more about it here, regarding the Leica 25mm f/1.4 lens.

      It is because of the internal focus design of the 19mm lens. Due to this design, you will have the "breathing" effect as the lens focuses. The 20mm lens does not have internal focus, which avoids the breathing problem, but, rather, it focuses slowly.

      So this effect is a result of the design of the 19mm lens, and impossible to avoid.

      However, newer cameras like the GH4 focus the 19 lens faster and with less jogging back and forth to verify the focus, and reduce the problem.

      Delete
  8. Thank you for the reply! I failed to identify "the jitter" as focus breathing because it looked so different than the focus breathing of the Leica 25mm f/1.4. More like a small vibration (I can't figure better word for it), e.g. noticeable on the fence above the railway tracks in your AF comparison video. But now when I look again at your video I begin to figure it out :)

    I am very happy with the video AF of my Panasonic G X Vario 14-42mm Power OIS lens (on GH3), but I mainly film indoors and would need a bit faster aperture for the occasions when I don't have the chance to use extra lights. I most often use the wider end of the lens, 14-22mm. I know it's a shame but at times I need to use AF for video...
    Do you have any suggestions on what would be the better lens(es) of the MFT lens selection for video AF?

    ReplyDelete
    Replies
    1. There are no safe lenses in that respect. All lenses can suffer from some focus breathing or other effects when using the AF during video recording. However, the cameras get better. With the DFD technology, the GH4 is better at focusing Panasonic Lumix lenses.

      See a comparison between the GH3 and GH4 here, using some common lenses. As you see, the Lumix G 20mm f/1.7 lens does quite well on the GH4.

      But one is never going to be completely safe with AF during video. For the best results, use manual focus.

      Delete