Just to speed things up a bit for everyone…
For those of you thinking about using Canon’s 200mm f/2.8 lens with a 2x extender on an APS-C body (like a Rebel or 7D)… don’t. Your images will be unusable. Chromatic aberration is simply out of control.
For those wanting to use the combo on a full frame camera (Canon or Sony)… absolutely do. You’ll get lovely and sharp images.
If you look at the first image you’ll notice a huge amount of chromatic aberration (also known as color fringing) in all of the background and around the raven. This amount of aberration is what you should expect with all of your photos when using the 200mm f/2.8 with 2x extender on an APS-C camera body.
The images are unusable, and you’ll see that with the next two images even when chromatic aberration is reduced the images are only okay at best. Chromatic aberration is still occurring and creating unnatural / unappealing colors in the background.
All of this chromatic aberration is due to the nature of the lens… it is not a fundamental flaw in either the camera, extender, or lens.
The optical formulas of lenses are adjusted to create a balance between reducing chromatic aberration, sharpness, and bokeh. You cannot have perfection in all things… And for the 200mm f/2.8 lens, it was not built to be used on both an APS-C camera body with a telephoto extender.
It was built to do one or the other, not both.
Chromatic aberration reduction simply took a back seat when the 200mm f/2.8 was designed… The 200mm was all about sharpness and bokeh.
Use the 200mm on a full frame camera body with or without an extender and you’ll find that there’s little chromatic aberration while being insanely sharp.
In other words, contrary to reviews, Canon’s 1.4x and 2x extenders are not often what’s causing poor images. People are simply using the wrong combination of lens, extender, and camera body.
Canon’s extenders absolutely do degrade image quality, that is inevitable, but they are not the horrible useless hockey pucks that some reviewers seem to think.
And the Canon 200mm lens is a perfect example of that complex interplay between lenses, cameras, and extenders.
Again, in short, do not use a 2x extender with the 200mm f/2.8 lens, on an APS-C camera body.
Pop that sucker on a full frame camera.