Achieving a DxOMark Score of 26 overall the Canon EF 135mm f/2L USM ranks reasonably highly on the DxOMark ratings for Canon compatible telephoto prime lenses. As you would hope for a prime the individual Lens Metric Scores indicate it’s a bright lens with a Transmission score of 2.3Tstop and there’s very little Distortion or Chromatic Aberration noticeable as illustrated by Lens Metric Scores of 0.1% and 4um respectively.
That said it only ranks 74th for all lenses tested on the DxOMark database and it’s not the best performing telephoto prime we’ve seen for Canon DSLRS either. The DxOMark Scores for telephoto primes tested on the Canon EOS 1Ds Mark III confirm the Canon EF 135mm f/2L USM ranks 5th overall behind competition from Sigma, Carl Zeiss, Samyang as well as Canon’s own EF 100mm f/2 USM.
With an overall Lens Metric Score for Sharpness of 14 P-Mpix the Canon EF 135 f/2L USM ranks mid-table for a prime tested on the Canon EOS 5D Mark II and its sharpness is comparable to the Canon EF 100mm f/2 USM Score of 14 P-Mpix.
Putting that into context further the Canon EF 135mm f/2L is a long way off the Sigma 85mm f/1.4 EX DG HSM, which achieves 17 P-Mpix for sharpness, but it does significantly out trump the Tamron SP AF180mm F/3.5 Di LD (IF) MACRO 1:1 Canon that only manages 9 P-Mpix.
Delivering best sharpness at apertures between f/2.8 and f/8 by the time you close down to f/11 sharpness does tail off slightly and although still reasonable at f/16 shooting with very small apertures like f/22 & f/36 are to be avoided. Sharpness at f/2 is not brilliant either but this is to be expected at such a wide aperture and simply closing down 1-stop to f/2.8 will improve things considerably.
|Canon 135mm f/2L USM|
If you’re buying this lens for creative shallow depth of field effects using f/2 then vignetting is an issue you should be aware of. It is optically very difficult to control edge shading at such wide apertures and the Canon EF 135mm f/2L USM is no exception with -1.33EV of shading at f/2. Close down to f/4 however and the problem is removed completely and doesn’t resurface at small apertures like f/32 either.