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Comparison with Sony 10-18mm zoom
on December 19, 2012
Sony seems to have a well thought-out product strategy for their NEX series bodies, which are proving to be a big hit. But their lens strategy is scattered. There is not a simple lens roadmap, but a mixture of lenses from different sources, some probably designed inhouse by Sony, some with the Zeiss name (and big price premium for that name), and other lenses which appear to be made for Sony by specialty third parties. This is partly because e-mount is not just for the NEX consumer cameras but also for Sony's line of high end professional video cameras. This is why Zeiss makes some extremely expensive cinema lenses in e-mount; $21K for a zoom!
But this scattered offering confuses their list of ultra-wide e-mount lenses for the consumer cameras. This compact 16mm f2.8 was the first kit lens offered by Sony. Then Sony added an Ultrawide converter attachment for this (VDL-ECU1) which has an effective focal length about 12.5mm. These two, when attached together, are actually quite good optically, for a total price about 300 bucks if you got the 16 in a kit. In addition, there is the Fisheye Converter (ECL-ECF1) which has a 180° field (distorted) for just 129 more dollars. These were clearly designed as a group and are actually quite brilliant. Unfortunately Sony has not really explained this to the customer base.
Recently Sony came out with the 10-18 mm zoom, f4, with image stabilization, but quite expensive at $850; a completely different approach.
Now having all of these at hand, I performed a direct image quality comparison. To compare the 10-18mm zoom to the 16mm, I set both to f4. Then I added the Ultrawide and matched the field of view by setting the zoom to 12.5mm. I didn't bother to compare the Fisheye to the 10-18 mm zoom because the latter cannot match its field of view.
These were all JPEGs, not RAW. It is important to understand that modern lenses such as both of these Sony's are no longer just hunks of glass; they are designed to be used with the in-camera JPEG processing firmware, which undoes the inherent distortions found in most wide angle lenses. Vignetting is also corrected, and chromatic aberration. It is no longer necessary to depend on the difficult correction of glass elements with additional glass elements, aspherics, etc.. Lenses now can no longer be separated from their software and this is having a tremendous impact on design and cost. This digital image processing can easily be observed in action on both these lenses when one is looking at the LCD and fires the shot and then sees the replay image come up right after, with the whole field jumping to altered shape by software distortion correction. For this reason it would require a lot of skill and Photoshop time to do the same thing manually starting from the RAW images. JPEG's are the way these lenses are designed to be used, so that's how they should be tested.
A summary of my tests of the image quality from the 10-18mm zoom vs. the 16mm (including the converter) is that they are roughly comparable. If I focus in the corners (to compensate for field curvature), the 10-18 is somewhat better than the 16. Surprisingly, the 16mm+Ultrawide converter images are very good.
Which should you buy? Photographers on a budget will do just fine with the 16 mm plus the Ultrawide converter. The 16 is very compact. Of course it's inconvenient to attach the converter if you are in a hurry, but the availability of the Fisheye is also a big plus and can't be matched by the 10-18 zoom. The three pieces taken together constitute an innovative and cost effective set. I don't know why Sony does not do a better job of promoting them.
The 10-18mm zoom is a fine lens but only moderately optically superior to the little guys. It costs three times as much as the 16+converter and is physically much larger. However, it's more convenient and quicker; having a zoom allows you to frame your shots and optimize the sensor area. Also image stabilization, unusual on an ultra-wide, more than offsets the one-stop smaller aperture, permitting slower shutter speeds, and is very much worth having.
The 16 and 10-18 lenses are different in many ways - size, cost, convenience, operational quickness - but image quality is not drastically different. If you can't decide, I recommend the 16mm plus the two converters. I put my NEX in movie mode with the Fisheye attached and walked around a party we were having, stopping for conversations and recording the whole feel of the event - fantastic footage which would be difficult to capture any other way.