#1. "RE: D800 file sizes" In response to Reply # 0
I am having trouble understanding your question. I don't know what a "medium" jpg is. When I save JPEG files, I give them a length and width, as well as a resolution. They are all exactly the same size.
As for use in a low light gym shooting sports, I give the nod to the D600 over the D800. Though both will be quite superior to the D300 in terms of noise performance. The D800 may well seem slow to you for frame rate, and the D600 may seem slow for focus performance. Then again, it may not. Rent or borrow one for a weekend and see.
#2. "RE: D800 file sizes" In response to Reply # 0
Honestly, having had a D800 since June and a D700 for 2 years prior I'd go with the D700 for indoor sports. Mostly for frame rate and similar low light level performance. Cheaper, too. And you won't have to worry about file size.
I've shot some football recently with the D800. Made me want to go running back to a D700 or even a D300. Not saying it can't be done -- it most certainly can be. Just that the D800 and D600 are not your only (best) choices.
If you're selling pics, I'd definitely consider a D3 or D3s before going with a D600/800 for sports.
#3. "RE: D800 file sizes" In response to Reply # 0
I shoot the D800 and my raw file size ranges from 38-48 mb right out of the camera. I processed some images yesterday as medium jpegs (quality 10 in image processing out of bridge) my files range from 3-6 mb at 300 ppi.
I also came from a D300 and the raw file size is quite a jump. It works for me, but it's way more than most people need or want. As far as the D800 itself as far as function and quality of picture I love it. I warn you there will be a learning curve shooting with it and shooting sports with it will definitely take some time to adjust to.