Review by Klaus Schroiff, published November 2005

special thanks to Rob (1st sample) and Markus Stamm (2nd sample)!

Introduction

The optical design of the lens is made of 14 elements in 12 groups including three UD elements. Typical for all true macro lenses it features a floating system for better close-focus correction. The min. focus distance is 0.48m resulting in a max. object magnification of 1:1. The aperture mechanism features 8 aperture blades. Due to the complexity introduced by the macro feature the lens is somewhat longer (83x187mm) and heavier (1090g) than conventional medium tele lenses such as the EF 200mm f/2.8 USM L. The filter size is 72mm.

The lens accepts all Canon EF tele-converters resulting either in a 252mm f/4.5 (180mm + 1.4x) or 360mm f/7 (180mm + EF 2x) combination. When used with these converters the max. object magnification increases accordingly - 1.4:1 with the EF 1.4x and 2:1 with the EF 2x converter. Most EOS cameras except the pro grade bodies will not provide AF with the EF 2x combo anymore because it exceeds the required max. aperture of f/5.6.

The mechanical quality of the lens is excellent - the outer barrel as well as the detachable tripod mount are made of metal and the very broad rubberized focus ring is very smooth and well damped. The lens is a true IF design so it doesn't change its length during focusing.
The AF performance of the lens is a little odd. If the camera is lost somewhere in focus nirvana it takes forever to focus throughout the focus range (with forever being about 4-5secs on the old EOS 350D). However, if the AF starts in the proximity of the focus point it's actually very quick. So it's something like having a lens with two gears here. In any case it is a good idea to take advantage of the focus limiter if you're using the 180mm f/3.5L for mainstream photography. For macro work it's probably a good idea to pre-focus to give the AF a guidance (if you really want to use AF for this purpose anyway). The focus range can be limited to either 0.48m-∞ or 1.5m-∞. The lens uses a near silent ring-type USM drive which is usually renowned for a very fast AF but obviously its incarnation here is a bit of an exception to the rule. Full-time manual focusing is possible in one-shot AF mode.