Introduction

Canon EF 20-35mm f/3.5-4.5 USM, released back in mind 1993, replaced Canon's EF 20-35mm f/2.8L USM as a consumer-grade variant (the original 20-35mm f/2.8L USM was in turn discontinued in favor of EF 17-35mm f/2.8L USM). The lens is priced at about US$370 when new (as of January 2008) and used copies go for about US$220 on used markets like eBay.

The optical construction of the lens consists of 12 elements in 11 groups - quite a complex formula when you think about it. The lens does not feature any special glass elements, this is probably because Canon was put cost as the primary consideration for this lens, to make it more affordable for regular users. The build quality is OK and resembles quality of all other, consumer-grade, Canon lenses. The internal cams of the lens wobble a little bit, but both focusing and zoom rings are pretty smooth (the lens features an electronic aperture control, so there's no dedicated aperture ring and all settings have to be controlled through your camera). The zoom ring is fully rubberized and is comfortable to grip, but the focusing ring is rather narrow. The lens sports an inner focusing design, so the lens cams do not extend during zooming or focusing.

Canon EF 20-35mm f/3.5-4.5 USM is a compact, but somewhat bulky lens, measuring 84 x 69mm (3.3 x 2.7in) and weighing 340g (12oz). The lens also features a fast and silent USM-type AF system along with a fully manual focusing. The shooting mode can be controlled by an AF/MF switch on the side of the barrel. The minimum focusing distance is 34cm (1.1ft), giving magnification of 1:7.7, the filter size is 77mm and the minimum aperture is f/27. The lens has a rather unusually looking front diaphragm, which is positioned behind the first lens element and is designed to cut out stray light, thus reducing flare. This is an interesting idea, but I'm not sure it can be as effective as a regular lens hood.

 

Image

 

The factory box includes Canon EF 20-35mm f/3.5-4.5 USM lens, front and rear caps, manual and registration cards. The lens is compatible with Canon's Gelatin Filter Adapters III and IV, and extension tubes EF 12 II and EF 25 II. The lens accepts optional EF-83II lens hood and you can use LP1214 soft lens case (also optional). The lens carries EF designation and thus is designed for full frame cameras. When used on APS-C bodies like Canon Digital Rebel XTi with 1.6x crop factor, the field of view of the lens resembles that of a 32-56mm lens on a full frame body - a rather narrow and unimaginative zoom range if you ask me.

 

Summary
Lens Composition 12 elements in 11 groups
Angular Field 94-63 degrees
Minimum Focus 34cm/1.1ft
Focusing Action AF/MF, USM
f-stop Scale f/3.5-f/27, camera-controlled
Filter Size 77mm
Lens Hood N/AEW-83II (optional)
Weight 340g/12oz
Dimensions 84x69mm/3.3x2.7"
Lens Case LP1214 (optional)

 

Field Tests

Canon EF 20-35mm f/3.5-4.5 USM produced quite decent results in the field. While it was not the sharpest wide angle zoom I have tried, it did showcase pretty solid performance in the center. Even border performance was pretty decent in the f/5.6-f/11 range (I would even say that image quality was better then with some of Canon's older wide angle primes). Color representation was somewhat on a warmer side, which is quite typical of Canon's lenses, and images did not seem to carry enough contrast - there was no 'punch' that would make you think that the objects are truly 3D.

 

Vignetting @ f/3.5 - full frame vs 1.6x crop (20mm)
Vignetting @ f/3.5 - full frame vs 1.6x crop (20mm)

 

Vignetting @ f/4.5 - full frame vs 1.6x crop (35mm)
Vignetting @ f/4.5 - full frame vs 1.6x crop (35mm)

 

The lens produced mild vignetting on a full frame Canon 5D at 20mm with wide open aperture. As you move toward the longer end of the zoom range, vignetting is reduced and by 35mm it's practically not even noticeable. On the other hand, the lens did not produce any significant vignetting on an APS-C body. Stopping down the lens obviously helps reduce vignetting and from f/5.6 through the rest of the aperture range vignetting is non-existent. Surprisingly (for a wide angle), the lens did not show significant color fringing on either APS-C and FF bodies (some color fringing exists around borders, but it's not the worst one can see in a wide angle). On a not so positive note, the lens showed goodly amount of barrel distortion at 20mm, which is reduced (and is practically non-existent) towards the longer end of the zoom. Finally, the lens also showed good handling of flare (looks like that unusual diaphragm does actually help here).

 

ISO 100, 1/2000, f/3.5, 20mm (100% crop)
ISO 100, 1/2000, f/3.5, 20mm (100% crop)

 

Canon EF 20-35mm f/3.5-4.5 USM image gallery...

 

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.

 

Canon APS-C: Canon EF 20-35mm f/3.5-4.5 USM showed rather interesting performance in the lab. The lens produced pretty solid results in the center pretty much across the entire zoom range. Performance was at its best in the f/5.6-f/8 range and somewhat worse at the ends of the tested aperture range. Image sharpness around borders with wide open apertures was unimaginative at best, but improved once stopped down to f/5.6. Overall, the lens showed most balanced results in the f/5.6-f/8 range where it is capable of delivering excellent 16in and decent 19in prints. Conclusion? The results come as a surprise since I certainly did not expect much from this relatively old (in terms of design) and inexpensive UWA zoom. AF system was pretty accurate and reasonably fast, although (and this is typical of most AF systems) it hunted in low light.

 

MTF50 (Line Width/Inch on the Print) @ 20mm
MTF50 (Line Width/Inch on the Print) @ 20mm

 

Normalized raw MTF50 @ 20mm
Normalized raw MTF50 @ 20mm

 

MTF50 (Line Width/Inch on the Print) @ 28mm
MTF50 (Line Width/Inch on the Print) @ 28mm

 

Normalized raw MTF50 @ 28mm
Normalized raw MTF50 @ 28mm

 

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

 

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

 

The lens showed decent handling of chromatic aberration on an APS-C camera. Center CA was quite low, never exceeding ~0.5px throughout the zoom range and all aperture settings. CA around borders was somewhat higher, averaging ~1px across the zoom and aperture ranges. Still, for a wide angle zoom lens CA can be considered quite moderate.

 

Chromatic Aberration (APS-C): Center
Chromatic Aberration (APS-C): Center

 

Chromatic Aberration (APS-C): Borders
Chromatic Aberration (APS-C): Borders

 

Here are 100% crops taken with Canon Digital Rebel XTi, comparing image borders at 20mm, 28mm and 35mm.

 

Image borders @ 20mm (100% crop): f/3.5 vs f/8
Image borders @ 20mm (100% crop): f/3.5 vs f/8

 

Image borders @ 28mm (100% crop): f/4 vs f/8
Image borders @ 28mm (100% crop): f/4 vs f/8

 

Image borders @ 35mm (100% crop): f/4.5 vs f/8
Image borders @ 35mm (100% crop): f/4.5 vs f/8

 

Canon FF: The lens continued to produce very decent, for a wide angle zoom that is, results even on a full frame body. Performance in the center was quite solid throughout the zoom range and across all tested aperture settings. Borders were slightly better at 20mm across all apertures, but in general, the lens seems to have a sweet spot in the f/5.6-f/8 range, where performance peaks across entire zoom range. Conclusion? Well, in absolute terms, performance is certainly not the best but it is good enough. The lens clearly benefits from a conservative zoom ratio and relatively slow speed, you just need to stop down the lens to achieve best results.

 

Normalized raw MTF50 @ 20mm
Normalized raw MTF50 @ 20mm

 

Normalized raw MTF50 @ 28mm
Normalized raw MTF50 @ 28mm

 

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

 

CA on a full frame body was under control with CA in the center averaging ~0.4px. CA around borders was higher, especially at wide aperture settings. At 20mm, CA hovers around 1.2px in the f/3.5-f/f/5.6 aperture range, but then drops to a more manageable ~0.8px. CA around borders drops to ~0.7px in the 28-35mm zoom range (and remains at about that level throughout the testes apertures).

 

Chromatic Aberration (FF): Center
Chromatic Aberration (FF): Center

 

Chromatic Aberration (FF): Borders
Chromatic Aberration (FF): Borders

 

Here are 100% crops taken with Canon 5D, comparing image borders at 20mm, 28mm and 35mm.

 

Image borders @ 20mm (100% crop): f/3.5 vs f/8
Image borders @ 20mm (100% crop): f/3.5 vs f/8

 

Image borders @ 28mm (100% crop): f/4 vs f/8
Image borders @ 28mm (100% crop): f/4 vs f/8

 

Image borders @ 35mm (100% crop): f/4.5 vs f/8
Image borders @ 35mm (100% crop): f/4.5 vs f/8

 

Alternatives

Canon EF 20-35mm f/3.5-4.5 USM is one of the oldest designs in Canon's current (as of Feb 2008) lineup. In addition to the EF 20-35mm f/3.5-5.6 USM, Canon currently offers three other wide angle zooms, one of which, Canon EF-S 10-22mm f/3.5-4.5 USM (review) is designed for APS-C type cameras with cropped sensor like Digital Rebel XTi, while the remaining two, Canon EF 17-40mm f/4L USM (review) and Canon EF 16-35mm f/2.8L II USM (review), are both full frame lenses. The good news is that all three lenses showcase very solid, for wide angle zooms, performance. Not so good new is that all three cost significantly more then the EF 20-35mm lens with EF 17-40mm f/4L USM being the 'cheapest' (priced at ~US$600) out of the three. Outside of the Canon lens camp, you might want to take a look at Sigma's 12-24mm f/4-5.6 EX DG ASPH HSM (review) and at 10-20mm f/4-5.6 EX DC HSM (review) assuming you are using an APS-C body. Both of these lenses are capable of producing pretty decent results and are also priced more aggressively when compared to Canon lenses. Finally, Tokina's AT-X PRO DX AF 12-24 f/4 (review) is one other wide angle zoom that is also worth taking look at.

 

Recommendation

Well, the lens is not what I would call a 'high performance' lens, but then again it was never expected to be. What it offers though is a good trade-off between image and build quality and price. The lens clearly has its shortcomings - barrel distortion at 20mm, some vignetting and most importantly, very short, by todays standards, zoom range. The zoom range will especially affect those of you using an APS-C body. And considering that there are dedicated EF-S and EF lenses that will produce better image quality and will give you better command over wide angle photography, this lens seems to be even more outdated.