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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 results : Sharpness 15mm / Sharpness 50mm / Sharpness 85mm / Geometry / Vignetting


Canon EF-S 15-85mm IS USM Geometric distortion

To measure the Canon EF-S 15-85mm IS USM's geometric distortion, we photographed a chart consisting of a grid pattern with the lens set to its shortest and longest focal lengths at an aperture of f8. The images were shot in RAW mode to avoid any in-camera corrections, then analysed with Imatest using 5th Order line calculation, and the full areas presented here at a reduced resolution. Smaller percentages are better. Results for other general-purpose lenses are shown at the bottom of this page; note the results for the EF-S 18-55mm here are for the older non-IS version.



Canon EF-S 15-85mm IS USM distortion zoomed-out
 
Canon EF-S 15-85mm IS USM distortion zoomed-in
EF-S 15-85mm IS USM at 15mm f8
Distortion: 4.65% barrel
EF-S 15-85mm IS USM at 85mm f8
Distortion: 0.545% pincushion


With the Canon EF-S 15-85mm IS USM zoomed-out to 15mm, barrel distortion was measured at 4.65%. Looking at the image above left, the wide-angle distortion looks quite significant, but it's important to put it into context by comparing it with the results for other general purpose lenses below.

Its predecessor, the EF-S 17-85mm IS USM scored 5.71%, while the EF-S 18-200mm IS super-zoom weighed-in with a considerable 6%. The EF-S 18-135mm IS fared better with 5.24%, but that still ranks all three as having noticeably worse geometric distortion when zoomed-out – and remember not only is the EF-S 15-85mm IS USM delivering less distortion than these other general-purpose lenses, but it's doing it with a wider focal length too. Note the EF-S 18-55mm kit lens performed best of all with just 3.35%, but it also has the shortest overall range.

With the EF-S 15-85mm IS USM zoomed-into 85mm, pincushion distortion was measured at 0.545%, which is almost twice as good as its predecessor, the EF-S 17-85mm IS USM, at the same focal length. The EF-S 18-200mm IS performed worst of all in this regard with a considerable 1.2% distortion when fully zoomed-in, but this was at 200mm and it's not an unusual result for a lens with this kind of super-zoom range. The EF-S 18-135mm IS also suffers from quite noticeable distortion of 1.19% when zoomed-into 135mm. Once again, the short range of the EF-S 18-55mm allows it to enjoy respectably minor distortion, although at 0.389% when zoomed-in, the EF-S 15-85mm IS USM isn't far behind.

So while distortion may be visible in the samples from the EF-S 15-85mm IS USM above, it's measurably and visibly superior to many other Canon general-purpose lenses. We're not surprised to find the EF-S 18-200mm IS suffering the worst with its super-zoom range, nor the EF-S 18-135mm IS with its fairly long range and low price, but the really revealing comparison is with the older EF-S 17-85mm IS USM. The newer EF-S 15-85mm IS USM boasts lower distortion than its predecessor when zoomed-in or out, and the latter is particularly impressive given the wider coverage.

For the record, the EF-S 15-85mm IS USM also performs fairly well in terms of geometric distortion when compared to equivalent models for rival systems: the Nikkor DX 16-85mm VR scored 5.32% and 0.907%, the Sony DT 16-80mm scored 4.04% and 0.52% and the Olympus ZD 12-60mm scored 2.31% and 0.45%.

Now let's see how the lenses compare in terms of light fall-off in the corners in our Canon EF-S 15-85mm IS USM vignetting results.

Canon EF-S 15-85mm IS USM Geometric distortion compared to other lenses

Canon EF-S 18-55mm f/3.5-5.6 distortion wide / tele
 
Canon EF-S 17-85mm f/4-5.6 IS USM distortion wide / tele
 
 
 
EF-S 18-55mm at 18mm f8
Distortion: 3.35% barrel
 
EF-S 18-55mm at 55mm f8
Distortion: 0.389% pincushion
 
EF-S 17-85mm IS at 17mm f8
Distortion: 5.71% barrel
 
EF-S 17-85mm IS at 85mm f8
Distortion: 0.967% pincushion


Canon EF-S 18-135mm f/3.5-5.6 IS distortion wide / tele
 
Canon EF-S 18-200mm f/3.5-5.6 IS distortion wide / tele
 
 
 
EF-S 18-135mm IS at 18mm f8
Distortion: 5.24% barrel
 
EF-S 18-135mm IS at 135mm f8
Distortion: 1.19% pincushion
 
EF-S 18-200mm IS at 18mm f8
Distortion: 6% barrel
 
EF-S 18-200mm IS at 200mm f8
Distortion: 1.2% pincushion


Canon EF-S 15-85mm IS USM results : Sharpness 15mm / Sharpness 50mm / Sharpness 85mm / Geometry / Vignetting


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