Most recent model cameras will do about as well with cropping as they will with a 2X extender in terms of image quality unless you are using very good glass and even then the image quality takes a big hit. I have EF 200 f2 along with EF 300 and 400 f2.8 primes which are some of the sharpest glass C
The Canon EF 2x II Extender is relatively small and light. It is weather-sealed when used with similarly-sealed lenses and camera bodies. Build quality is excellent - Canon L Lens quality. Pictured above from left to right are the Canon Extender EF 1.4x Converter , Canon Extender EF 2x Converter and the Canon 24-70mm f/2.8L USM Lens .

You mention using the EF 70-200mm f/2.8L IS USM "II" lens That works well with the EF "III" Extenders. It might also work well with the EF "II" Extenders, but is not something I've ever tried. (I have use the EF 1.4X II on the EF 100-400mm II with excellent results.) I have no idea how that lens

Yes, that lens is fully compatible with your Rebel. It exceeds the capability of your camera. Depending on what current lens you have the image quality will be equal or better. Whether or not you get great photos depends on you.
7D + EF 2x III + 70-200 USM IS II. Hi, I own a 7D and and a 1DX, shoot sports with the 70-200 L IS USM II and sometimes use the 1.4 extender III. I chose not no purchase the 2X extender because I will lose 2 light stops. I find that the lens/camera combo perform faster focusing without the extender.
Question: Am I severely handicapping myself, resolution wise, by using a Canon 70-200 f2.8 II with a Canon 2x converter on my Canon 7d mark2? - Stephen S. [youtube . 167 388 45 175 186 248 286 358 193

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