Hello! I have a question concerning the crop factor and the aperture of a given lens. I can't remember where I read that but in a review about the Panasonic 22mm f/1.7 lens, the reviewer said that the aperture was the 35mm equivalent of a 3.4. Is it true? I'm wondering because my brother has a Sony A57 (crop factor 1.5) with a lens that has an apterture 2.8. So, I was looking to have something at least similar beacuse I like the performance in low light of his lens. Any idea about that? Thanks!