p.1 #1Comparison of 300mm 2.8 vs 400mm 2.8 with same framing on humans?
I saw an excellent video on YouTube comparing the 300mm 2.8 GM and 400mm 2.8 GM on felines and wildlife. Are there any comparison of track and field and other sports with equal framing such that the 300mm photos are taken closer to the subject to fill the frame the same as the 400mm?
p.1 #2Comparison of 300mm 2.8 vs 400mm 2.8 with same framing on humans?
Camera to subject distance has an effect on the perspective of an image regardless of the lens used. If your framing was the same then that distance was different and you may see some effect from that.