I notice a lot of recommendations for prime lenses for sports photography - I love prime lenses (I have the 35mm 1.4) but it seems like for something such as sports, being stuck at a fixed focal length would be tough. So my question is to those of you shooting telephoto primes such as the 135mm - do you just take the shot where ever the subject happens to be in your view finder and crop to get your shot later? I understand when taking a group photo or something like that, its easy to "zoom with your feet." But being in bleachers and trying to capture fast moving action isnt as easy to do that.