Quite a bit. 300mm definitely has its limitations. I have a canon tc1.4 that I've had some success with but I feel like I need a TON of light for that.
I'm not quite sure. There was a group of them scouring the ground. This one hopped up on the tree and started rooting around. :) He was scratching himself just prior LOL
For my children's sporting events a 300 f4 is a little too long at times. I pretty much have all access since I help coach all of them!, so I'm usually better off mounting an 85 f1.8 and getting down on the sidelines.
Both. completely depends on what you need.
I'll never shot a full frame digital but I still would rather have ef lenses if at all possible. there are some perfectly acceptable ef-s options.
Way to many variables! a night scene shot at ISO 6400 might look like garbage. a properly exposed bird in flight shot at ISO 6400 might look superb. and everything in between. The more you shoot the more you learn.