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Canon EF-S 15-85mm f3.5-5.6 IS USM Gordon Laing, February 2010
 
 

Canon EF-S 15-85mm IS USM coverage and stabilisation

Canon's EF-S 15-85mm IS is designed as a general-purpose lens for cropped-frame bodies delivering equivalent coverage of 24-136mm. To illustrate this range in practice we fitted the lens to an EOS 7D body, mounted it on a tripod and shot the same scene fully zoomed-out, then fully zoomed-in.


Canon EF-S 15-85mm IS USM coverage
EF-S 15-85mm at 15mm (24mm equivalent)
EF-S 15-85mm at 85mm (136mm equivalent)

At the wide-end, 24mm captures a comfortably wider field-of-view than the typical 27 or 28mm of most kit lenses, allowing you to squeeze-in larger subjects and ideal for cramped interiors or situations when you can't step back any further. It also allows for more dramatic perspective effects than 28mm lenses.

Three or four millimetres may not sound like much, but it makes a big difference in wide-angle terms, and this capability is the big selling point the EF-S 15-85mm IS has over its predecessor, the EF-S 17-85mm IS.

As you zoom the lens in, you'll go through most of the classic focal lengths for portrait photography, and while the average aperture won't deliver very shallow depth-of-field effects, it's still possible to nicely blur the background – you can see an example in our gallery, and for technical advice on achieving this effect, see our Portrait Tutorial.

The maximum equivalent focal length of 136mm also allows you to grab detail shots or close-range action and wildlife, although if you'd like to enlarge distant subjects you'll want something much longer.

To put the wide-angle coverage into perspective, we've pictured it below with red frames indicating the coverage you'd achieve with the older EF-S 17-85mm IS and EF-S 18-55mm IS lenses when also zoomed-out. These frames do not represent theoretical comparisons which have been generated mathematically. Instead they were generated by over-laying actual photos taken with each lens just moments apart, and scaling them in Photoshop until the details lined-up (taking geometric distortion into account). So the differences you see here really are what you'd experience in practice. Note, the actual coverage is indicated by the outside edge of the frame.

Canon EF-S 15-85mm IS USM wide-angle coverage comparison
EF-S 15-85mm at 15mm (24mm equivalent)
Red frame represents actual coverage of EF-S 17-85mm at 17mm
EF-S 15-85mm at 15mm (24mm equivalent)
Red frame represents actual coverage of EF-S 18-55mm at 18mm

The frames clearly indicate the wide-angle benefit of the EF-S 15-85mm IS over the other two lenses. It's comfortably wider than its predecessor and much more so than the standard kit lens. Again a few millimetres may not sound liek much written down, but can make a world of difference in reality.

We performed the same comparison against the older EF-S 17-85mm IS with both lenses zoomed-in, and despite sharing the same maximum focal length in their specifications, the newer EF-S 15-85mm IS actually captured a fractionally tighter field of view. This is a very minor difference though, mentioned here only as a matter of interest. When shrunk to the size shown on this page the difference essentially becomes imperceptible.

 
Canon EF-S 15-85mm IS USM Stabilisation

   
   



 

The Canon EF-S 15-85mm IS is equipped with Image Stabilisation capabilities to counteract camera shake. Like all of Canon’s IS lenses to date, this employs an optical system which means you see the stabilising effect while composing through the optical viewfinder. Seeing the image suddenly steady itself when you half-press the shutter release button is very reassuring, especially when you’re shooting at longer focal lengths.

IS is enabled by flicking a switch on the side of the lens barrel. Canon claims the lens has four stops of compensation and automatically detects panning to temporarily deactivate one axis. In operation, the IS motor is very quiet.

To put its effectiveness to the test we took a series of photos with it zoomed-into an equivalent of 136mm, where traditional photographic advice would recommend a shutter speed of at least 1/136 to eliminate camera shake.

Our sequence started at 1/125 and reduced by one stop each time until 1/8. We performed this sequence twice, first without IS enabled, and secondly with IS enabled. Below are 100% crops taken from the non-IS and IS images at a shutter speed of 1/15.

Canon EF-S 15-85mm IS USM Image Stabilisation
EF-S 15-85mm at 85mm (136mm equivalent) IS off, 1/15
EF-S 15-85mm at 85mm (136mm equivalent) IS on, 1/15

On the conditions of the day, the fastest we could handhold a sharp result when fully zoomed-in without any stabilisation was at 1/60; anything slower suffered from camera shake. With IS enabled, we could match the sharpness under the same conditions at a shutter speed of 1/15. You can see examples taken at 1/15 with and without stabilisation above, and it’s clear how the version with IS is much steadier.

This corresponds to two stops in practice over our 1/60 shot, or approximately three stops over conventional wisdom at 1/136. This falls short of the four stops claimed by Canon, and indeed when repeating stabilisation tests under different conditions we still found the lens failing to deliver much more than two stops in practice.

While two stops is still a valuable facility to have at your disposal, it's a little disappointing compared to the three or four stops we've measured in practice with other systems. When framing with IS enabled, the view also appeared to wobble from time to time more than expected, perhaps suggesting a fault with our model or the automatic mechanism which disables one or both axes of stabilisation when panning or mounted on a tripod. Indeed the eerily quiet IS motor on this lens made us wonder at times if it was enabled at all, but listening very closely confirmed it whirring very faintly in the background.

We were surprised by the modest results here, as earlier Canon stabilisation systems always proved very effective in our tests. Supplies of this lens were limited in our region at the time of writing, but we hope to retest the IS capability on other models in the future. In the meantime, if you own this lens, we'd be interested to hear your personal experiences in the Camera Labs forum.

Now it’s time to see how the lens performs against alternative general purpose zooms in our Canon EF-S 15-85mm IS results pages.


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