I must admit that I have pretty much stuck to zooms. I have rented both the 35L and 85L but am no means a "prime" expert.
So, here I find myself about ready to press the buy button on expensive primes like the 35L, 135L, etc. But I keep asking myself if I'm ready for them.
Sometimes I wonder if I should just get my feet wet first with say a 85/1.8 and then go from there. When then I ask myself, what about a low-light lens on the wide side? And then I can only think of the 35L. I have the impression that the 35F2 and the like are rubbish, so why bother? Perhaps I am wrong.
Anyway, what was your first prime? Did you start of slow or jump right in and get the expensive stuff?

