Introduction

Canon EF 17-40mm f/4L USM is one of Canon's professional grade lenses, first released in May of 2003. It is one of only four ultra wide zoom lenses Canon manufactures at this time. Sporting three aspherical lens elements and a Super UD glass element, the lens construction is made of 9 groups and 12 elements. The lens offers full-time manual and a ring-type USM auto-focus (the AF is extremely fast and quiet), with a focusing distance of only 28cm (11 inches), with a maximum magnification of 1.4x at 40mm. Priced at approximately $700 in the U.S. (as of January 2007), the lens has captured attention of both professional and pro-sumer photographers alike.

 

Image

 

On APS-C digital SLR cameras with 1.6x crop ratio, the lens' field of view resembles that of a 27-64mm standard zoom lens. The lens is compatible with Canon's EF mount, which means you will be able to use it with Canon's traditional 35mm film SLR cameras as well as with all of Canon's modern dSLR cameras.

Canon EF 17-40mm f/4L USM is relatively compact and lightweight (475g/16.8oz, 83.5x96.8mm/3.3x3.8in). The build quality is outstanding, as expected from Canon's professional grade L lenses - the lens is environmentally sealed against dust and moisture, focus and zoom rings are smooth, with no wobbling whatsoever and focus mode switch is tight, preventing you from accidentally switching it when holding the lens. The petal-shaped lens hood is somewhat shallow which makes it less effective with APS-C dSLRs. On the positive side, the front element of the lens does not rotate, which allows attaching filters to the filter mounting thread on the front of the lens and you can still use a polarizer with the hood attached. The filter size is 77mm, which means you should be prepared to spend a small fortune on filters. The outer length of the lens remains constant throughout all zoom ranges, which is another plus. There is also a gelatin filter holder at the rear of the lens.

The lens is compatible with Canon's Extension Tubes EF 12 and EF 25, which can give the following camera-to-subject distance and image magnification:

Camera-to-Subject Distance Magnification
Near Far Near Far
EF12 17mm 155 159 0.83x 0.70x
40mm 206 271 0.59x 0.32x
EF25 17mm Incompatible Incompatible
40mm 196 218 1.02x 0.70x

The factory box includes Canon EF 17-40mm f/4L USM lens, lens case LP1319, lens hood EW-83E, front and rear lens caps, manual and registration card.

Summary
Lens Composition 12 elements in 9 groups
Angular Field 104-57 degrees
Minimum Focus 28cm/0.9ft
Focusing Action AF/MF, USM
f-stop Scale f/4-f/22, camera-controlled
Filter Size 77mm
Lens Hood EW-83E (included)
Weight 475g/16.8oz
Dimensions 83.5x96.8mm/3.3x3.8"
Lens Case LP1319 (included)

 

Field Tests

Canon EF 17-40mm f/4L USM delivers dramatic perspective at 17mm - a dream for landscape photographers! Overall, images taken with Canon EF 17-40mm f/4L USM are very sharp in the center with some softness at the border. Stopping down to f/5.6 seems to help and images are sharp across all focal lengths with very vivid colors and exceptional contrast. When shooting close objects (the closest focusing distance is 0.28m/0.92'), leaving the lens wide open will produce a very nice background blur, giving you the opportunity to play with the depth of field.

The lens does not have Image Stabilizer and is somewhat slower then Canon's other ultra-wide zoom L lens - the EF 16-35mm f/2.8L USM. Using a tripod in situations requiring long exposures (such as low light photography) is highly recommended. The shallow hood which comes with the lens is practically useless - it does not really help you protect the lens. For digital SLR cameras with reduced sensors, the hood does not help improve image quality in sunlight and you might want to consider using a longer lens hood to keep out stray light.

 

Vignetting @ f/4 - full frame vs 1.6x crop (17mm)
Vignetting @ f/4 - full frame vs 1.6x crop (17mm)

 

Vignetting @ f/4 - full frame vs 1.6x crop (40mm)
Vignetting @ f/4 - full frame vs 1.6x crop (40mm)

 

Despite its relatively slow maximum aperture, Canon EF 17-40mm f/4L USM shows noticeable vignetting on a full-frame camera at 17mm with wide open aperture. Vignetting is reduced by f/5.6 and practically disappears by f/8. Vignetting is also reduced towards the longer end of the zoom range. The lens shows basically no vignetting throughout the zoom on an APS-C camera. The lens did not show any significant color fringing and withstood flare quite nicely. Distortion was moderate on a full frame body at 17mm, disappearing around between 24-35mm and was very minor on an APS-C body, naturally benefiting from the crop introduced by a smaller sensor.

 

ISO 100, 1/1250, f/4, 17mm
ISO 100, 1/1250, f/4, 17mm


 

Lab Tests

Please note that MTF50 results for APS-C and Full-Frame cameras are not cross-comparable despite the same normalized [0:1] range used to report results for both types of cameras.

Two lens samples were tested in the lab. The results varied between samples, with center performance variance averaging ~4% and border performance variance averaging ~23% across all apertures and zoom range. The review includes results from the second sample, which showed better overall performance.

 

Canon APS-C: Canon EF 17-40mm f/4L USM produced pretty solid results in the lab (for an ultra wide zoom lens that is). Overall, the lens showed better performance in the 24-35mm zoom range and suffered a bit at wider and longer ands of the zoom. The lens was quite sharp in the center, with excellent performance throughout the zoom and almost all aperture levels. Border performance in general lags somewhat behind. The lens shows most balanced results across the entire zoom in the f/5.6-f/8 range, where the lens is capable of producing outstanding 19in and very decent 24in prints. Conclusion? Producing some of the best results in the ultra-wide zoom segment, Canon EF 17-40mm f/4L USM is a worthy competitor, truly earning its L designation.

 

MTF50 (Line Width/Inch on the Print) @ 17mm
MTF50 (Line Width/Inch on the Print) @ 17mm

 

Normalized raw MTF50 @ 17mm
Normalized raw MTF50 @ 17mm

 

MTF50 (Line Width/Inch on the Print) @ 24mm
MTF50 (Line Width/Inch on the Print) @ 24mm

 

Normalized raw MTF50 @ 24mm
Normalized raw MTF50 @ 24mm

 

MTF50 (Line Width/Inch on the Print) @ 35mm
MTF50 (Line Width/Inch on the Print) @ 35mm

 

Normalized raw MTF50 @ 35mm
Normalized raw MTF50 @ 35mm

 

MTF50 (Line Width/Inch on the Print) @ 40mm
MTF50 (Line Width/Inch on the Print) @ 40mm

 

Normalized raw MTF50 @ 40mm
Normalized raw MTF50 @ 40mm

 

Chromatic aberration was more or less under control and with the exception of 17mm focal length, the lens produced pretty minimal CA. Even at 17mm Canon EF 17-40mm f/4L USM produced quite decent (for an ultra-wide lens) results with CA not exceeding 1.5 pixels around borders and practically no CA in the center. Unfortunately, stopping down did not really help and the lens continued to produce some chromatic aberration (not a major problem since CA in general can be easily fixed with image processing software like Photoshop).

 

Image borders @ 17mm (100% crop): f/4 vs f/8
Image borders @ 17mm (100% crop): f/4 vs f/8

 

Image borders @ 24mm (100% crop): f/4 vs f/8
Image borders @ 24mm (100% crop): f/4 vs f/8

 

Image borders @ 35mm (100% crop): f/4 vs f/8
Image borders @ 35mm (100% crop): f/4 vs f/8

 

Image borders @ 40mm (100% crop): f/4 vs f/8
Image borders @ 40mm (100% crop): f/4 vs f/8

 

Canon FF: Canon EF 17-40mm f/4L USM showed pretty solid performance on a full frame body, with excellent center performance throughout the zoom range. Border performance struggled a bit at f/4 pretty much throughout the zoom, but once stopped down to f/5.6 quality improved, reaching quite respectable levels. Like with an APS-C body, the lens showed more balanced results across the supported zoom range in the f/5.6-f/8 range. Conclusion? Some weakness around borders at f/4, but overall pretty solid performance for a wide angle zoom. This is surely a winner.

 

Normalized raw MTF50 @ 17mm
Normalized raw MTF50 @ 17mm

 

Normalized raw MTF50 @ 24mm
Normalized raw MTF50 @ 24mm

 

Normalized raw MTF50 @ 35mm
Normalized raw MTF50 @ 35mm

 

Normalized raw MTF50 @ 40mm
Normalized raw MTF50 @ 40mm

 

Chromatic aberration on a full-frame body was quite low in the center - CA here did not exceed ~0.5px at 17mm and was slightly lower throughout the rest of the zoom range. Unfortunately, CA crept up higher around borders, especially at wider end of the zoom. At 17mm CA averaged ~1px at f/4, dropping to more manageable 0.7px towards f/11. Moving towards longer end of the zoom reduced CA but not by much - at f/4 CA averages ~0.7px and remains at about that level throughout the rest of the aperture range.

 

Image borders @ 17mm (100% crop): f/4 vs f/8
Image borders @ 17mm (100% crop): f/4 vs f/8

 

Image borders @ 24mm (100% crop): f/4 vs f/8
Image borders @ 24mm (100% crop): f/4 vs f/8

 

Image borders @ 35mm (100% crop): f/4 vs f/8
Image borders @ 35mm (100% crop): f/4 vs f/8

 

Image borders @ 40mm (100% crop): f/4 vs f/8
Image borders @ 40mm (100% crop): f/4 vs f/8

 

Alternatives

There are not that many high quality, affordable ultra-wide zoom lenses available on the market. One possible alternative to Canon EF 17-40mm f/4L USM that falls within the same price range is Canon EF-S 10-22mm f/3.5-4.5 USM (review), which resembles a 16-35mm lens on a traditional full-frame camera. This is the only ultra-wide lens Canon specifically designed for APS-C type cameras. The lens exhibits very decent performance characteristics albeit shows some softness at the borders (review). Another possible alternative is Sigma AF 10-20mm f/4-5.8 EX HSM DC, which is also specifically designed for APS-C cameras with reduced image circle. While this lens is cheaper than Canon's, it exhibits some distortion throughout entire focal length (review). Finally, if you are willing to spend a small fortune on a high-quality ultra-wide zoom lens, then Canon EF 16-35mm f/2.8L USM is also highly recommended (review).

 

Recommendation

Canon EF 17-40mm f/4L USM is probably one of the best ultra-wide zoom lenses available on the market. For APS-C type cameras, the lens looses its ultra-wide appeal but still remains a solid choice for serious amateurs. Given its relatively affordable price, outstanding construction and image quality, the lens is a great value for your money.