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Canon EF-S 18-135mm f3.5-5.6 IS Gordon Laing, February 2010
 

Canon 18-135mm results : Sharpness 18mm / Sharpness 50mm / Sharpness 85mm / Sharpness 135mm / Geometry / Vignetting


Canon EF-S 18-135mm IS Geometric distortion

To measure the Canon EF-S 18-135mm IS'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 18-135mm IS distortion zoomed-out
 
Canon EF-S 18-135mm IS distortion zoomed-in
EF-S 18-135mm IS at 18mm f8
Distortion: 5.24% barrel
EF-S 18-135mm IS at 135mm f8
Distortion: 1.19% pincushion


With the Canon EF-S 18-135mm IS zoomed-out to 18mm, barrel distortion was measured at 5.24%. 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.

The high-end EF-S 15-85mm IS USM enjoyed lower distortion when zoomed-out with a measurement of 4.65%. The EF-S 18-200mm IS super-zoom suffered from worse distortion with a measurement of 6% when zoomed-out. You may be interested to discover the EF-S 18-55mm actually scored the lowest distortion when zoomed-out at just 3.35%, although this is because it also has the shortest optical range.

In fact with the exception of the older EF-S 17-85mm IS USM which suffers from above average distortion when zoomed-out, you'll notice a pattern emerging: lenses with longer focal ranges generally suffer from worse distortion. As such it's no surprise to find the EF-S 18-135mm IS suffering fairly badly in this test with only the EF-S 18-200mm IS super-zoom performing any worse.

The same optical theory applies when all the lenses are zoomed-in: generally those with longer focal ranges perform worse than those with shorter ranges. So once again the EF-S 15-85mm IS USM (and its predecessor) do better than the EF-S 18-135mm IS, and the EF-S 18-55mm does best of all, leaving the EF-S 18-200mm IS to deliver the worst result here. Do take a closer look at the actual numbers though as the EF-S 18-200mm IS is only just behind the EF-S 18-135mm IS when both are zoomed-out, and again the EF-S 15-85mm IS USM out-performs the earlier EF-S 17-85mm IS USM.

So the EF-S 18-135mm IS suffers from quite noticeable geometric distortion when zoomed-in or out, although again this is the price you normally pay when dealing with a lens with a long optical range. Poor geometry can be improved in software, but only after significant wrangling of the pixels in your image, potentially reducing the quality. So if you're into photographing subjects with straight lines near the edges of your frame, such as buildings, then be warned they could look a little bendy with this lens.

Now let's see how the lenses compare in terms of light fall-off in the corners in our Canon EF-S 18-135mm IS vignetting results.

Canon EF-S 18-135mm IS 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 15-85mm f/3.5-5.6 IS USM distortion wide / tele
 
Canon EF-S 18-200mm f/3.5-5.6 IS distortion wide / tele
 
 
 
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
 
EF-S 18-200mm IS at 18mm f8
Distortion: 6% barrel
 
EF-S 18-200mm IS at 200mm f8
Distortion: 1.2% pincushion


Canon 18-135mm results : Sharpness 18mm / Sharpness 50mm / Sharpness 85mm / Sharpness 135mm / Geometry / Vignetting


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