Canon EF-S 15-85mm f/3.5-5.6 IS USM
 

Canon EF-S 15-85mm f/3.5-5.6 IS USM

This review covers


PAGE 2

» Image Quality «


PAGE 3

» Sample Pictures «

» Conclusion «

» Further Information «


Table of contents

Image Qualityhide all test shotsshow all test shots

Note: the test shots for each of the image quality tests can be compared directly amongst all tested lenses. Within the test box click on "Choose lens to compare with..." to add a lens to the comparison. Then use your mouse to hover over the lens thumbnails. If all those test shots are a little too overwhelming consider clicking on "hide all test shots" above this paragraph.

Sharpness / Resolution

The EF-S 15-85mm f/3.5-5.6 IS USM is a very sharp lens. The resolution is highest at the tele end of the focal range but it's good throughout. It is a lot better than the kit lens EF-S 18-55mm f/3.5-5.6 IS II and also better than the EF-S 18-135mm f/3.5-5.6 IS. If you consider full frame EF lenses it has a resolution that's very much like the EF 24-105mm f/4L IS USM (on APS-C cameras) - which is an L series lens! Note that Canon (so far) do not give the L series tag to any of their EF-S lenses (probably to suggest that pros should go with full frame bodies).

-Test shots

APS-C    tested with 7D
Sharpness / Resolution

Distortion

At 24 mm effective focal length the EF-S 15-85mm f/3.5-5.6 IS USM shows a massive amount of barrel distortion. That's not nice but consider that this lens is wider by a couple of mm than say the kit lens EF-S 18-55mm f/3.5-5.6 IS II. But of course even at 24 mm lenses can perform much better in regard to distortion. Compare with the similarly priced EF-S 10-22mm f/3.5-4.5 USM at the same focal length to see how well distortion could be under control. Unfortunately distortion cannot be reduced by stopping down so if you need a distortion free picture go for longer focal lengths (or correct it in post). At 35 mm (effective) and upwards the EF-S 15-85mm f/3.5-5.6 IS USM shows only slight barrel (and from 50 mm pincushion) distortion.

-Test shots

APS-C    tested with 7D
Distortion
Aperture:
Irrelevant

Crop from top of image (downsized)

Crop from bottom of image (downsized)

Best case: the line between the black and white boxes is completely straight in both test shot crops

Color Errors Transverse Chromatic Aberrations

At 50 mm and 70 mm effective focal length the EF-S 15-85mm f/3.5-5.6 IS USM shows moderate color errors. At all other focal lengths the color errors are quite intense and they cannot be reduced by stopping-down. The performance is better than that of the EF-S 18-55mm f/3.5-5.6 IS II and the EF-S 18-135mm f/3.5-5.6 IS but it is not good.

-Test shots

APS-C    tested with 7D
Color Errors

Crop from lower image border
(in landscape orientation)

Color errors in focused parts of the image (upscaled)

 

Best case: no color fringes

Crop from left image border
(in landscape orientation)

Beauty of blurred image parts Bokeh and Axial CA

Fortunately the EF-S 15-85mm f/3.5-5.6 IS USM has an evenly circular aperture shape. This is ideal to get nice and even out-of-focus blur. Canon achieve that by using 7 aperture blades of the circular type. Even more important the lens's performance in regard to color fringes in those out-of-focus areas of the image is outstanding. Even at maximum aperture hardly any color fringes are noticeable. Only at 50 mm and 70 mm effective focal length the EF-S 15-85mm f/3.5-5.6 IS USM shows slight color fringes that already fade after stopping down a single stop.

-Test shots

The way blurred parts of the image look depends on several things such as focal length, aperture setting, aperture shape, distance to the background, distance between foreground and background as well as the texture and dynamic range of the background. With so many things to consider it's very difficult to compare different lenses. Moreover the beauty of blurred image parts is also a matter of personal taste.

In general blurred image parts should be as uniformly blurred as possible and ideally not show any artifacts. Out of the above mentioned criteria only the shape of the aperture cannot be influenced by the photographer and thus this test will show you the shape you are dealing with (left test image). To minimize artifacts there should be no bright line around the edge of the aperture shape. To get uniform blur the aperture should be as circular as possible (which depends on the number of aperture blades used and their individual shape). Furthermore there should be no color fringes in out-of-focus areas of the image (middle and right test shots).

Aperture Shape

Number of aperture blades:  7
Type: circular
Best case: circular and evenly bright

Color errors in out-of-focus areas of the image (upscaled)

before focal plane

behind focal plane

Crops from the center of the image
Best case: no color fringes in out-of-focus areas

Curvature of the focal plane Field Curvature

From 24 mm to around 50 mm effective focal length the EF-S 15-85mm f/3.5-5.6 IS USM struggles with curvature of the focal plane. To reduce it you will have to use very high f-stops like f/11. Whether or not curvature is a problem for you depends a lot on what your subject is. If it's a straight wall that you'd like to capture from the left to the right image border you are in trouble (on the other hand a shot like this might be done using high f-stops anyway). In most real-life applications though you will use the focus more selectively and since the lens doesn't suffer from soft corners you'll have no trouble positioning your subject anywhere in the image. But getting everything in focus from the corner to the center at once will be difficult with this lens if you aim for the low f-stops.

-Test shots

Crop from the corner of the image
focused at the image corner

 

Best case:
no difference

Crop from the corner of the image
focused at the image center

Corner Shadow Vignetting

At wide focal lengths such as 24 mm (effective) any lens shows intense corner shadows - that's plain physics and cannot be avoided. Having said that the EF-S 15-85mm f/3.5-5.6 IS USM actually performs pretty well at 24 mm. Compare with the EF-S 10-22mm f/3.5-4.5 USM at the same focal length or the full frame L series lens EF 24-105mm f/4L IS USM (compare that one with the full frame setting to be fair) and you'll notice that the EF-S 15-85mm f/3.5-5.6 IS USM's corner shadows are less pronounced. At longer focal lengths the lens shows less and less corner shadow until from around 70 mm it is no longer noticeable.

-Test shots

APS-C    tested with 7D
Corner Shadow

Crops (100%)

Corner

Center

Best case: no difference in brightness

Test shot (downsized)

Corner

Center

Best case: perfectly even brightness

Result-Chart

Best case: no color gradient

EV

0

-1

-2

-3

-4

-5

PAGE 1

Handling

PAGE 2

Image Quality

PAGE 3

Conclusion

 

top