Monday, June 9, 2014

Canon EF-S 10-18mm f/4.5-5.6 IS STM

Few things live up to the designation "no-brainer."  Nikon's consumer range has something of that sort in the AF-S 35mm f/1.8G DX, which has the dual virtues of being both sharp and extremely affordable. It could be said that Canon's EF-S 50mm f/1.8 comes close to that ideal, but as incredibly inexpensive as that lens is, it simply won't let you forget that it is a cheap lens.

The  EF-S 10-18mm f/4.5-5.6 IS STM is a good candidate for being an insta-buy lens for crop-frame Canon users. At just under $300 USD, it has a MSRP that is $180 less than the former low-cost ultra-wide champ, the Sigma 10-20mm f/4-5.6 EX DC HSM. If you compare it against its big brother, the Canon EF-S 10-22mm f/3.5-4.5 USM, the 10-18mm is half the cost. If that was the only selling proposition, it would be enough... but low cost isn't its only virtue.

Design and Features

The variable-aperture of f/4.5-5.6 is expected for this price point and focal length, but the inclusion of IS image stabilization makes this a unique lens in the APS-C ultra-wide zoom category. Though manufacturer's usually quote a 4-stop advantage to their stabilization systems, its best to use a conservative figure of two stops when calculating your safe hand-held shutter speed. In this case, the IS system turned on gives the still shooting equivalent of a f/2.2-2.8 lens compared to having the system turned off; this is slightly brighter than the constant aperture Tokina 11-16mm f/2.8 over the same focal range. 

That is definitely a good thing, but it's not the huge advantage that it seems to be. In absolute terms, if you take the advantage as being two stops, the minimum safe shutter speeds would be 1/4s to 1/7s between the wides and long end of the lens. To put this into perspective, most image stabilization systems, no matter how effective they are, tend to run into a performance floor around 1/10s. To put this into perspective, a four-stop advantage at the wide end of the lens implies a safe hand-holding shutter speed of 1 second; the IS will help, but it's not going to give you the exact equivalent steadiness under the most extreme conditions.

Though most advanced shooters will not see it as a major advantage, the 10-18mm STM is extremely light; it's made of the same composite plastic that the 18-55mm STM is made of. In terms of weight and length, it is comparable to that kit 18-55mm STM lens which is bundled with the T5i (EOS 700D) and the SL1. (Make sure that your camera firmware is up to date for the T5i.) On those lightweight cameras, this lens balances well and does not overwhelm the body; you would be hard pressed to tell by the heft of this lens that there are 14 glass elements inside. The front takes 67mm filters, and as per all of the STM lenses, the focus ring is an all-electronic affair. Though not up to professional qualities, the lens built with fairly tight tolerances. There isn't any wobble in the extendable lens barrel and the zoom ring lacks resistance but does turn smoothly. A disappointment is that the lens mount is not metal, making the 10-18mm more like that 18-55mm STM lens than the more upscale 18-135mm cousin. It should be noted that a metal lens mount is not always the sign of quality that many people think it is: many lenses that use metal flange mounts still have those mounts screwed down onto what is essentially a plastic chassis.

Left: 18-55mm STM     Right:10-18mm STM
Given the price, weight and budget-friendly construction, it's possible that we will see the 10-18mm lens bundled with Canon's entry-level DSLR's in the future. However, the video-friendly nature of this lens makes it a natural choice for the EOS 70D's advanced Dual-Pixel autofocus system.

Canon 10-18mm STM on EOS 70D

What makes STM lenses video friendly? Compared to USM lenses (or even worse, the non-USM lenses) STM lenses are nearly silent and focus with extremely smooth motions. This smoothness comes at the expense of outright speed, but under normal non-professional shooting, these lenses are fast enough. The quietness of the operation can't be emphasized enough, as it means that there is no noise for the on-camera microphones to pick up. (That only begs the question of why you are using the on-camera microphone...)

Here is an example of the focus operation of the 10-18mm STM versus the Sigma 10-20mm f/3.5 DC HSM. Sigma's HSM mechanism is similar in concept to Canon's USM motors. In this case, the Sigma motors produce an audible chatter that the on-board microphone turns into a grinding noise:

Note also that the IS image stabilization system, though working, does not cancel out motion caused by handshake. For effective video, there is no substitute for proper camera mounting and good technique, but for casual users, the inclusion of IS will turn shaky video into watchable video.

Optics and Image Quality

For $300 USD, you wouldn't expect perfection, but the lens does produce pleasing and usable images. The (likely) target audience will be more than happy with the image quality, as the Canon JPEG engine does correct for geometric distorion and other maladies. The overall impression of the images is that the rendition is fairly consistent across the frame once corrected, and that there aren't really any significant problems to worry about. Is it critically sharp? No, but the results seem to be ever so slightly more pleasing than with Sigma 10-20mm f/4-5.6 DC HSM. If you are shooting at flat targets, the corners don't seem to be critically sharp as you would expect with a higher grade lens, but this is much less of an issue with non-flat subject matter. Here's an example of the difference in width that 10mm and 18mm give:

10mm, f/5
18mm, f/5.6

Both of the above samples were taken from out of camera JPEG's. What's remarkable is that there is not much more barrel distortion at 10mm in the RAW file. The same goes for 18mm: yes, there is geometric distortion control being applied, but it's not as much as you would expect for such an inexpensive lens. Do note that the vignetting is quite visible at 10mm.

Here's a sense of the exaggeration in depth that is possible with this lens. Unfortunately, unlike the 10-22mm, the 10-18mm's longest focal length is still a bit too wide for street-shooting and smaller groups of people. Once again, you can see the vignetting at 10mm that you don't at 18mm. 

10mm, f/5
18mm, f/5.6

Again, though not the most crisp results, the 10-18mm does an admirable job for its price point.

Concluding Thoughts

Often, the triggering even for a photographer to acquire an ultra-wide zoom is travel to a scenic destination with expansive vistas. This hints at what happens afterwards; when the vacation is over, the ultra-wide sees less use and the normal zoom becomes the "walk-around" lens of choice. This is unavoidable, as the majority of casual photography falls between 16-80mm on APS-C formats. Knowing this, it makes little sense to splurge on a lens that sees limited use. (Many photographers know this and still do it regardless!) What the 10-18mm has done is to remove to lower the barrier of acquisition for a lens that is off the beaten path for many photographers, so much so that it seems inevitable that the 10-18mm will cannibalize some of the 10-22mm's revenues.

Though it seems like a losing proposition for Canon to replace sales of a higher cost item with sales of a lower cost one, the barrier to entry is now so low that it is conceivable that Canon will make up the difference in unit volume. After all, one of the truest maxims of business is to cannibalize your own sales with something new/better... before somebody else does.

With thanks to Broadway Camera

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