佳能镜头Canon EF 180mm f35 L USM macroReviewTest Report

1、IntroductionThe Canon EF 180mm f/3.5 L USM macro is the longest tele macro lens currently available from Canon. The lens was introduced back in 1996 without any direct predecessor. Its primary application is, obviously, macro photography but naturally it's not limited to that. On APS-C DSLRs the

2、 field-of-view is equivalent to 288mm on the classic full-format. 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 result

3、ing 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 72m

4、m. 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

5、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

6、 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 t

7、he 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 photogr

8、aphy. 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

9、 obviously its incarnation here is a bit of an exception to the rule. Full-time manual focusing is possible in one-shot AF mode. DistortionsAs to be expected from a true macro lens the level of distortions is absolutely negligible. 180mm:The chart above has a real-world size of about 120x80cm. Vigne

10、ttingWhen using the lens on an APS-C DSLR there's only a slight degree of vignetting at f/3.5 which shouldn't be problem in most scenes and it's a non-issue at other aperture settings. MTF (resolution)In the lab the EF 180mm f/3.5 USM L macro showed a very good performance from f/3.5 til

11、l f/16. Beyond diffraction effects are the limiting factor - the f/32 figures are not shown below because there's only an image soup left at this setting. The lens showed a very even performance across the frame without any obvious centering issues. Nonetheless the MTF figures are a little disap

12、pointing for a Canon L grade tele lens - more so regarding its price tag. Two lenses have been tested and the results were near-identical. Possibly the performance may be better at close-focus distances but for mainstream photography this is about what you can expect from a valid sample of this lens

13、. Below is a simplified summary of the formal findings. The chart shows in line widths per picture height (LW/PH) which can be taken as a quantity for sharpness. If you want to know more about it you may check out the corresponding Imatest Explanations. Chromatic Aberrations (CAs)Similar to most oth

14、er fix-focal lenses chromatic aberrations (color shadows at harsh contrast transitions) are extremely low and nothing to worry about. Bokeh (out-of-focus blur)The quality of the bokeh is an important criteria for a tele lens and more so for a macro variant. This aspect of the EF 180mm f/3.5 USM L ha

15、s been frequently discussed in many web forums. At f/3.5 the lens is capable to produce nicely circular and uniform out-of-focus highlights. However, the situation changes when stopping down to f/5.6 where octagonal shapes start to appear. This is certainly "too early" for a macro lens whi

16、ch is usually used at medium aperture settings at macro distances. At f/3.5 the bokeh shows also some one-sides "smearing" towards the image borders (see the card portion) which doesn't look overly pleasing. This smearing occurs only in close proximity to the focus point though (see th

17、e quadrant). Here're two full size samples at f/3.5 and f/5.6. VerdictThe Canon EF 180mm f/3.5 USM L macro is an interesting lens with a very good optical performance and exceptional mechanical qualities. Nonetheless the lens wasn't really able to fulfill the high expectations associated wit

18、h a Canon L grade lens - there're even some zoom lenses performing better in terms of resolution. Beyond the resolution aspect the lens showed pretty perfect performance figures - minimal vignetting, next to non-existent distortions and marginal chromatic aberration. The bokeh, the quality of the out-of-focus blur is relatively decent although not stellar. The AF performance of the lens is a bit of a mixed bag. If the in-focus point is i