EF 85mm f/1.8 USM vs EF 100mm f/2 USM vs EF 135mm f/2L USM
First to make sure all know about these lenses, you should read these lenses review:
After you read the reviews, now you understand that these lenses have similar characteristic. They are fixed lenses and suitable for portrait categories. William L. Castleman has done some experiment with all these lenses. Because this review actually written by William L. Castleman, so I don’t have right to post any pictures in my blog. So you must go to this link to see the experiment setup and result. If you are boring to see any text there, you just see these link (I don’t recommend you only see the result, I think you should read the experiment setup, and some summary in the first link I give to you). I hope after you see this review and test result, you know what lens you need to buy; especially for portrait lens category. This is my opinion (someone please correct me if I am wrong), I think EF 85mm f/1.8 USM is “the optimal” choice, EF 135mm is “the best (in term of image quality)” choice, EF 100mm is “the one that I don’t recommend”. If you often to use “100mm” focal length, my suggestion is get the EF 100mm f/2.8 Macro 1:1. My opinion maybe right for someone and wrong for the other because everyone has different focal length that he often to use. Finally, any suggestions and comments are welcome.