I'm trying to decide between two lenses. The decision sort of boils down to mm and f-number... not sure what to go with. I use a Pentax K10D, which has a 1.5x crop. Pentax 40mm f/2.8 Limited Linkety Pentax 50mm f/1.4 Linkety So... the 50mm has better low-light capabilities, but the 40mm gives me a bit wider view and is physically much smaller. What suggestions, thoughts, etc. do you guys have?