Originally Posted by torifile
One more question about your stream shot, Rob, if you don't mind. I notice that you're using the wide end of your lens. I'm sure you've got other lenses that can shoot 24mm at f/2.8. Why did you choose that particular lens? The reason I ask is that I have a hard time deciding which lens to use when I have 2 lenses that cover a particular focal length and aperture. For instance, I've got a 17mm prime f/1.8 and a 12-40 f/2.8. In low light, it's not a question - the prime is the easy answer. But outside, when I don't need to stop down so far, I have a tough time deciding.
The answer is less exciting than you might think, because it depends on what else I want with me on a given outing. The camera bag used, and how much weight I'm willing to carry around are also factors. When it comes to picking a set of gear for an outing that's never easy, unless scouting of the shooting location has been done ahead of time. That is preferable, since it means you can take what you need, rather than guessing. For all around shooting, when I'm not sure what I'm going to encounter, the 24-70 F2.8 (equivalent to the 12-40mm) and 70-300mm VR zooms are packed. If I have something particular in mind I'll bring as little as possible, maybe just the 16-35mm VR, 50mm 1.8, 105mm macro or a F2.8 telephoto lens.
On the day I took the photo of the creek I wanted to carry specific equipment, because the workshop was kind of open ended. We were told to bring everything, which is not practical because a) it would be insanely heavy and b) There is not a bag out there that could manage all my gear anyway. On that outing I had two full frame bodies (less lens swapping, which is preferable when working around water), the 24-70, 105 macro and the 70-300. So the 24-70mm was what I had to work with on the wide end. As I said, not the most exciting reason.