I have a Sony SLTa55V, and I'm looking for a good wide angle lens. Currently, my most-often used glass is a Tamron AF 28-75mm f/2.8 SP XR Di LD Aspherical (IF) Lens. But sometimes, my subjects require more to be in frame. Specifically, I shoot museum dinosaur skeleton mounts, and am pretty serious about it. I've been doing a good deal of research, but frankly, can't decide on what lens would best fit my purpose of indoor, dark museum shots of entire dinosaur skeletons. To give you an idea, I'd like to be able to fit the entire mount of Giraffatitan as displayed in the Berlin Museum, in one shot. A quick google will clearly show you the scale I'm talking about.
Granted, I don't want to exhaust the bank account on this lens... It would really only be used for that rare, entire body shot, that most museums and their mounts aren't condusive for to begin with. But, I don't want to skip on quality, either. And it doesn't need to qualify as "wide angle"... 28mm (well, really 42mm), just doesn't cut it sometimes.
Any suggestions would be greatly appreciated.