“ If you had a choice between this new Tamron and the Canon f4 with IS which way would you go? The way I see it the trade off is between canon's build quality and one stop of light. I'm an amateur who is working to improve and have really liked shooting with a 50mm @ f1.8 compared to my other slower lenses. I shoot with an older canon body, the 40D which seems to do a good job for now so spending my money upgrading to great lenses that will be with me as I improve and learn is most important. ”