420-700mm f/8-10. 600-1,000mm f/11-14. Canon RF 70-200mm f/2.8 IS USM. Not compatible. Not compatible. Canon RF 28-70mm F2 L USM. Not compatible. Not compatible. While it’s obviously disappointing that the 70-200mm won’t work at all with the teleconverters, and the 100-500mm only half works, both the 600mm and 800mm primes are fully Model Overview. Built with distance in mind, the Canon EF 1.4x II Extender offers extra zoom for that all important moment. As an added extra to the lens, it provides excellent focal range without comprising quality. It offers a perfect lightweight option to mulitiply the focal length without investing in a new lens.
For comparison, these Double-crested Cormorants were shot in 2020 with the 5D mark IV using the EF 100-400mm L and EF 1.4X near the same place as above. 280 feet, 1/1000th, f/11, ISO 1000, 560mm. Double-crested Cormorants - 5D4 with EF 1.4X Extender. Osprey, 200 feet, 1/1250th, f/10, ISO 800, 700mm.
Bottom line and why I would prefer one of the 150-600mm super zooms , there is no substitute for having a lens with the actual focal length vs a tel-con. If you think of it this way, 50mm is one power. So, your 200mm lens is equivalent to a 4x power binocular. Adding the 1.4x tel-con and you now have abut a 5x binocular.
The lens and extender combo can always be used in manual focus mode. Meanwhile with the Canon Extender EF 1.4x II you can easly extend the focal length of compatible Canon L Series with very little degradation in the final digital picture. My advise is to go for the 1.4 extender.
Extending the effective focal length of select Sony E-mount telephoto lenses, the FE 1.4x Teleconverter increases the lens's magnification by 1.4x for a narrower field of view. The dedicated design maintains full communication between the lens and E-mount mirrorless cameras, including auto-exposure metering, autofocus, and Optical SteadyShot
To photograph the solar eclipse you'd be best to use the EF 100-400mm f/4.5-5.6L IS II USM stand alone with the EOS 60D and exclude the Extender 1.4x III. The reason being is that auto focus will not be available due to the stop loss in light in all but a handful of professional series cameras. From Canon's product page for the RF 1.4X extender: Note: This extender is only compatible with the following RF lenses RF100-400mm F5.6-8 IS USM, RF100-500mm F4.5-7.1 L IS USM, RF400mm F2.8 L IS USM, RF600mm F4 L IS USM, RF600mm F11 IS STM, RF800 F5.6 L IS USM, RF800mm F11 IS STM, RF1200mm F8 L IS
EF 1.4x III and EF2x III extenders are recommended for use with EOS Digital Cameras. *1: EOS-1D Mark II, EOS-1Ds Mark II, EOS-1D Mark II N, EOS-1D, EOS-1Ds. *2: EOS650, EOS620, EOS750, EOS750 QD, EOS850, EOS850 QD, EOS700, EOS10S/10, EOS REBEL/1000, EOS REBEL S/1000 F, EOS REBEL S QD/1000 FN QD, EOS ELAN/100, EOS630/600, EOS RT, EOS-1, EOS
