Canon EF 17-40mm f/4 L

This article reviews the full frame performance of the Canon EF 17-40mm f/4L lens. My intented use of the lens is for landscape photography with a Canon EOS-1Ds camera. The EF 17-40mm f/4L lens (left panel) is a very sharp, high contrast zoom lens with performance characteristics that often match and sometimes exceed those of quality prime lenses at wide angle. Performance drops off slightly in the corners at 35mm, but otherwise this lens is an outstanding performer at a very good price ($670, US Gray Market).

Canon EF 20mm f/2.8 (lower lens) and Sigma 20mm f/1.8 EX (upper lens) were also tested in this review

50% MTF Performance Data
Link to Methods Used MTF values should only be compared within a review and not between reviews since conditions varied between lens reviews for this test parameter.

The EF 17-40mm lens has microcontrast close to that of the Canon prime at 20mm. The Sigma 20mm prime performs poorly at the close focusing distance.

The EF 17-40mm lens has microcontrast close to (slightly better than) that of the Canon L-prime at 24mm.

The EF 17-40mm lens has microcontrast below that of Canon primes at 35mm.

Corner Image Sharpness and Chromatic Aberration with EOS-1Ds

Image sharpness and lateral chromatic aberration (CA) varied among the lenses tested. Mild lateral chromatic aberration in the far corners of images is a common finding in wide angle lenses used with the EOS-1Ds. Examples below in the table are from the upper left corner of this chart.

17mm and 20mm

24mm, 35mm and 40mm

Center Image Sharpness with EOS-1Ds

Central image sharpness varied among the lenses tested. There was no central chromatic aberration. Examples below in the table are from the center of this chart.

17mm and 20mm

24mm, 35mm and 40mm

Linear Distortion of the EF 17-40mm f/4 L lens

Light Drop Off (Vignetting)

The lenses tested all have significant light drop off from the center when shot at wide-open aperture. The table summarizes how image field illumination evens as aperture is closed.

17mm and 20mm

24mm, 35mm and 40mm

Building / Landscape Test Target at 20mm All lenses tested performed very well at this focal length.
Building / Landscape Test Target at 35mm Corner performance on the EF 17-40mm f/4L dropped off slightly at 35mm

Conclusions

If you shoot wide angle, full frame photographs with Canon cameras stopped down at f/8 and beyond, the EF 17-40mm f/4L lens is an outstanding lens. Contrast and sharpness are greatest at the wide end (20 and 24mm) of the zoom range and approach or exceed those of quality prime lenses. Sharpness drops off in far corners at 35mm and 40mm and microcontrast drops off slightly at 35mm. Performance drop at the long end of the zoom range is unlikely to be objectionable in most landscape photos. Linear distortion is present as expected for a 2.5x zoom. Overall, this is a high performance superwide angle zoom for full-frame Canon cameras as befits the "L-lens" designation.

• Notes on 20mm prime lenses:
  • Canon 20mm f/2.8 lens: Strengths: The lens is free of linear distortion. It has less light drop off when stopped down than the 17-40 lens. It is very useable at f/2.8 and f/4. Weaknesses: None
  • Sigma 20mm f/1.8 EX lens: Strengths: The lens is linear distortion free and has even illumination when stopped down. It provides sharp and high contrast images near infinity focus. Weaknesses: Images are very soft at f/1.8 and f/2. At close focusing range, the lens is not as sharp and has poor microcontrast (see 50% MTF scores) compared to other lenses tested at 20mm. Some people may not like the slightly yellow cast in color images.

Other reviews:

• Michael Reichmann mini-review comparing performance with the EF 16-35mm f/2.8 L lens

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© 2005, William L. Castleman
Initially posted 16 April, 2005