Question Regarding Extender(s)

Other than the obvious benefit of more range are there any other benefits/detriments between using a 1.4X III extender or a 2.0X III on a Canon 70-200 f/2.8 II?

Second question related to the above question: Does the camera matter? In this case 7D Mark II versus 6D Mark II?

Thank You.

You may already know this, but with the 1.4X you lose one stop of light so the widest aperture will be 4. With the 2X, you lose 2 stops so the widest aperture will be 5.6.

The Canon camera does not matter for optical performance, the specific model of lens does matter. For example, photozone.de used to routinely test Canon 70-200 in various vintages with Canon 1.4x teleconvertor, but discontinued the practice, I'm guesing why but perhaps it was too routine to see only about -10% loss of resolution with the extender. OTOH, some Canon lenses like the 100-400mm don't even handle FILTERS (!!!) well, as has been experienced by owners of the version 1 lens.

You may also see somwhat different results depending upon which manufacturer's telextender. I did a test almost 10 years ago, and found a Kenko slightly different from a Canon telextender...one was so slightly better in the center, the other was so slightly better on the edges of the frame.

The model of camera does matter about which cameras continue to try to autofocus at f/8...some models are limited to f/5.6 autofocus

Depending on the camera, loss of focusing speed is the main detriment to using extenders. IMO it is better to have the reach when you need it, but sometimes faster is better.

In this album, there are several images that are taken using an extender. When the focal length is listed as 600 mm, it's most likely the EF 300 mm f/2.8L IS II USM together with the EF 2X Extender III.

Ah, sorry, this forum can't link to that album, for some reason. This post is moot.