Fulvio; I have both wide and tele Mutars for my 3.5 F. I bought them when I was feeling flush. The tele is better than the wide but I don't use either anymore. The joy of a Rollei is the light weight and easy handling. The Mutar's are quite heavy and bulky off the front. I feel they are indeed "collector's items". Too much to carry around. I also find your photography improves when you only have one lens.