@ws wrote:
Ya the lens is pretty low end. It struggled a bit in shady conditions and the wing bluer was a bit much. The EOS 70 D comes with a 250mm lens versus the 300mm on my sons. Would the 250mm lens work better because of a more sensitive ISO range?The ISO ranges from something like 100-12000 where the one on my son's ranges from 100-600.
Thanks
The reasons to go with the 70D over a Rebel like your son's T5 is a better AF system, more frames take per second, and a larger buffer so you can take more pictures in a row.
I would choose the EF-S 55-250 IS STM over the EF 75-300 lens that it is likely that your son has. The STM lens will have better image quality, and also image stabilization (IS) which does help with birds not in flight.
Figure either of those lenses will be 'starter' lenses, and if you really get into birding you will eventually move up to the EF 100-400 L IS II or one of the 3rd party 150-500/600mm lenses.
To answer your original question the 70D can use all the same lenses as the T5 which includes all EF and EF-S lenses and compatible 3rd party lenses. Both the lenses you've asked about have the same maximum aperture of f/5.6 so ISOs will be similar. I believe the 70D has better high ISO performance than the T5 so coupled with the better image quality of the STM lens you should be able to crop a little further than you could with your son's setup.
