with a Canon EF 600mm f...4L IS III USM lens at 1...been using the EF 600mm f...L IS II USM and in future...will use the EF 600mm f...4L IS III USM. With birds, reach...is the Canon EF 70-200mm f/2.8L IS II USM – I use...improvements in the EF 600mm f...4L IS III USM (over the Mark...tailed eagle. The EF 600mm f...L IS II USM is an excellent...with the Mark III I get all