Nikon’s APS-C sensors measuring 24x16mm have a diagonal of 29mm, while full-frame sensors measuring 36×24 have a diagonal of 43mm, so the ratio difference between the two is approximately 1.5x. Canon’s APS-C sensors are slightly smaller and have a crop factor of 1.6x. For Canon R5 and R6 at least the autofocus is leading edge: using dual pixel autofocus in its latest iteration: Dual Pixel CMOS Autofocus II
That is incorrect. As OP implies, wildlife photographers have preferred APS-C for a while because of the greater magnification. Cropping full-frame will lose sharpness and resolution, so that is not a solution. Shooting at 600mm equivalent on an APS-C camera can be sharper than shooting 400mm on full-frame and discarding 50% of the pixels.
While the Canon EOS 90D is smaller and lighter than the full-frame models, it’s still a heavy and chunky camera, especially for APS-C sensor standards. However, that additional heft provides excellent balance when paired with the vast range of Canon EF lenses – just avoid the optically-unimpressive 18-135mm f/3.5-5.6 kit lens.
Higher-end APS-C cameras follow the same principles as micro 4/3rds, where they typically have the same specs as top-of-the-line full-frame cameras, but at half the cost. For example, the Canon 90D, released in 2020 has a 32.5-megapixel sensor, shoots 10fps as well as 4k30 all for just $1,200.
Full frame sensors are the same size as 35mm film, measuring 24 x 36mm. APS-C sensors are smaller at around 15 x 23mm, though the exact size can vary depending on the make. You might see APS-C aH3I. 712266571839496168243462
