Canon EF 70-300mm f/4-5.6L IS USM Lens Review

Canon EF 70-300mm f/4-5.6L IS USM Performance

At 70mm and f/4, sharpness already approaches excellent levels across the frame and with the aperture closed down to f/5.6 sharpness reaches those excellent levels across the frame.

Sharpness is remarkably consistent throughout the zoom range as can be seen with the lens zoomed to 135mm. Sharpness remains very good across the frame at maximum aperture and rises to excellent levels in the centre by f/5.6. Peak sharpness across the frame is achieved with the lens stopped down to f/8 for this focal length. Here clarity is excellent across the frame.

Finally, at 300mm the performance of this lens holds up well. Many lenses covering this range display a marked falloff in resolution at maximum telephoto, but this lens is still capable of producing very good sharpness in the centre of the frame and good sharpness towards the edges at f/5.6. Stopping down to f/8 produces excellent sharpness in the centre of the frame although the clarity towards the edges remains good.

Resolution at 70mm		Resolution at 135mm
Resolution at 300mm		How to read our charts The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column. The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple. For this review, the lens was tested on a Canon EOS 5D Mark III using Imatest.

Chromatic aberrations are very well controlled for a telephoto zoom lens covering this range, just exceeding 0.75 pixel widths at 70mm when stopped down to f/11 and f/16. Other aperture and zoom combinations result in lower levels of fringing that should pose few issues, even in large prints or harsh crops from the edges of the frame.

Chromatic aberration at 70mm		Chromatic aberration at 135mm
Chromatic aberration at 300mm		How to read our charts Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software. Apochromatic lenses have special lens elements aspheric, extra-low dispersion etc. to minimize the problem, hence they usually cost more. For this review, the lens was tested on a Canon EOS 5D Mark III using Imatest.

Falloff of illumination towards the corners of the frame is kept in check throughout the zoom range. The corners are consistently 1.39stops darker than the image centre at either end of the zoom and visually uniform illumination is achieved one full stop down from maximum aperture.

Distortion is pretty well controlled throughout the zoom range. At 70mm 1.74% barrel distortion is present, which is replaced by 1.66% pincushion distortion at 300mm. The distortion pattern is uniform across the frame, which should make applying corrections in image editing software afterwards relatively straightforward.

The supplied lens hood is very deep and does an excellent job of shading the front element, as well as protecting the lens from bumps and scrapes. Contrast remains high, even when shooting into the light and the lens is very resistant to flare, even when the hood isn't used.

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