Canon EF 24-105mm f/3.5-5.6 IS STM
Lab Test Results
January 5, 2015
by Andrew Alexander
Canon released the EF 24-105mm ƒ/3.5-5.6 IS STM in September of 2014, complementing its widely popular 24-105mm ƒ/4L. The lens features Canon's new STM (stepping motor) autofocus system, making it very useful for movie-making with its near-silent operation.
The 24-105mm isn't a ''constant'' lens, in that as you increase the focal length, the maximum aperture size decreases. The following table reflects the change in aperture size with focal length:
The EW-83M petal-shaped lens hood is available for around $25, but does not ship with the lens. The lens is available now for around $600.
The Canon 24-105mm ƒ/3.5-5.6 STM offers very sharp images when mounted on EF-S mount cameras, but that's mostly because those sensors don't see the underwhelming corner performance of the lens.
Mounted on our Canon 7D test camera, we see great performance even wide open at the wide angle (ƒ/3.5 and 24mm); stop down to ƒ/5.6 and you're looking at tack-sharp images across the frame. It's like this through to 50mm, though corners do get a little bit softer as you zoom in towards the telephoto range, where the lens struggles a bit. At 85mm and 105mm there is some corner softness present, and you'll need to stop down to ƒ/8 to improve it a bit; stopping down further doesn't offer any extra sharpness.
Mounted on the full-frame Canon 1Ds MkIII, we see the lens' true nature; it's significantly soft in the corners when used at its widest apertures, and you'll have to stop down significantly (ƒ/8 or ƒ/11) to get the best performance out of the lens.
On either camera body, there's no great incentive to stop down beyond ƒ/16, where diffraction limiting produces generalized softness across the frame (at 105mm and ƒ/36, we note some of the softest imagery we've seen in some time).
The lens performs well to resist chromatic aberration, though it can easily be found in the corners of images that show areas of high contrast. If you peep your pixels closely you'll see color shifts of green to magenta; for some reason, it's worst at the 70mm setting.
When mounted on subframe EF-S mount cameras, there isn't much corner shading to speak of -- the corners of an image are less than a quarter-stop darker than the center at any aperture and focal length.
On a full-frame camera body however, it's a different story entirely. When used at the wide-angle widest-aperture combination (24mm and ƒ/3.5) we see corners that are over a stop and a half darker than the center of an image. It's better at any other setting, but the 24mm will always show at least a half-stop differential, even stopped down dramatically.
As you'd expect with any wide-angle zoom lens, distortion is present in images shot with the Canon 24-105mm; we note barrel distortion between 24mm and 35mm, and pincushion distortion after 50mm. There's a sweet spot where distortion is minimized just after 35mm. Distortion is also more prevalent on full-frame images than on those taken with sub-frame cameras.
The Canon EF 24-105mm ƒ/3.5-5.6 IS STM employs an autofocus system called a "Stepping Motor", which allows the lens to provide smooth and quiet autofocus operation, which is particularly beneficial during video capture. The lens took around a second to focus from infinity to close-focus. It offers full-time manual operation by just turning the focus ring after autofocusing. Attached 77mm filters will not rotate during focus operations, making life easier for polarizer users.
The Canon EF 24-105mm offers better-than-average macro performance: a minimum close-focusing distance of 40 cm (just over a foot) and a magnification of 0.3x.
Build Quality and Handling
At just over 18 ounces, the Canon EF 24-105mm ƒ/3.5-5.6 IS STM makes a light package for the versatile range of focal lengths it offers. To accomplish this the lens is largely plastic, though it is of a high-quality construction. The lens mount is metal, while the 77mm filter threads appear to be plastic. There is no flexing or rattling when using the lens: the exterior of the lens has Canon's usual speckled finish, while the lens barrel, visible when the lens extends towards 105mm, is smooth. The only information available on the lens are marked focal lengths; there are no distance scales or depth-of-field indicators.
The lens has two primary switches: one to enable or disable autofocus (''AF/MF'') and one to activate or deactivate image stabilization (''Stabilizer ON/OFF''). There is a very slight sound when image stabilization is active, but mostly only audible when your ear is next to the lens.
The large zoom ring is the prominent feature of the lens, at just over 1 1/4 inches in width. The rubber texture is a series of raised ribs that provide an easy grip. The zoom action is smooth, going from 24mm to 105mm in a ninety-degree turn, with only a minor amount of force required to transition between focal lengths. The lens extends as it is zoomed out, adding an extra 1 3/4 inches to its overall length. Zoom creep was not a factor in our testing with this lens, though Canon has thoughtfully included a zoom lock switch in case over time the zoom action should loosen up.
The focusing ring is mounted near the front of the lens, with a plastic, 3/4-inch-wide ribbed grip. With the new STM focusing system, the lens focuses electrically, meaning there is no direct mechanical connection between turning the ring and the resulting focus. The focusing ring will turn forever in either direction and rotates easily, yet still offers a good amount of resistance for manual focus.
Canon claims up to four stops of hand-holding stabilization with its IS system, and our testing approaches that but puts it more at the three- to three-and-a-half stop range -- still, very good by any stretch.
The optional EW-83M lens hood is petal-shaped with a bayonet-mount, but we can't comment on its usefulness as it doesn't come with our test sample (nor does it come standard with the retail copy).
Canon EF 24-105mm ƒ/4L IS USM ~$1,200
A popular, general-purpose lens that's been around since 2005; the STM version is slightly sharper. The L-glass really shines in its resistance to chromatic aberration, however -- it's shows much better performance in the ƒ/4L. Both have image stabilization, though the new STM motor is probably more useful for movie making due to the quieter, smoother focusing.
Canon EF 28-135mm ƒ/3.5-5.6 IS USM ~$480
Another stalwart performer, but the 24-105mm STM is much sharper and more resistant to chromatic aberration. There's definite improvement in the new lens, and I would expect after 16 years of production this lens is close to being retired.
Sigma 24-105mm ƒ/4 DG OS HSM ~$900
Sigma's offering in this focal range is more of a competitor to the 24-105mm ƒ/4L, but for just a few dollars more than the 24-105mm STM it offers similar performance to the L-glass alternative.
It's a good lens for the money, and for the general consumer who's interested in taking photos and movies outdoors it will serve admirably -- fast autofocus, versatile zoom range and image stabilization. For those who want a wider aperture at telephoto, or who need a more rugged, weather-sealed build, they’ll have to invest in Canon’s more expensive L-series version. Generally though, this lens will do well to replace the 28-135mm as the kit lens for Canon bodies.
The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.
As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.
Canon EF 24-105mm f/3.5-5.6 IS STM
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