I went on a hike this past week with the Sony A900, and managed a couple of decent shots using the Konica Minolta AF 17-35mm F/2.8-4 exclusively. Go here for a fall color tour in the mountains near Tucson, AZ.
This lens works good, and produces sharp pictures, but man you won’t believe the flare and hosting, it’s horrendous! If the sun is anywhere near the image, you better have your hand ready, the hood doesn’t help, and if the sun is in the image, you’re screwed, period. Sometimes you can lose the ghosts in a background, but it’s going to be tough with this lens. I used a Tiffen G ND filter, and at 17mm it vignetted hard, and also caused more reflective problems.
I was reading Photoclub alpha’s recent entry on do you need the A900? and agree on his points. It’s pretty clear to me your problems and costs will go up exponentially from an APS-C system. One is the example above with the lens, (telephoto lenses seem ok with my limited use) the other is with files sizes. My average Fine JPEG is 7-8mb. My average extra fine JPEG is about 20mb!! I had a couple of JPEG images that were over 30mb themselves! RAW + JPEG will run 45-50mb. I’ve noticed battery power goes down faster when using quality setting which yield larger sizes, (the access lamp is on for 10 sec in RAW+JPEG). I’m getting about 300-400 shots per charge using fine, or extra fine, and no flash. Also, file sizes are larger when using Vivid settings, about 10% it seems. A 4gb card will give you about 200 shots in extra fine, and takes about 15 minutes for a memory stick pro duo to download. These are my personal observations so far.