Canon EF 200mm f/2.8 with 2x extender, I-version

The thing that triggered me to do this test in the first place, was a (pretty unbelievable) claim that I've seen on several occasions. The claim was, that using a 2x extender doesn't improve image quality. I think I can safely say, that this is not the case. At least there seems to be significant benefit with the 200mm f/2.8 lens, using a Canon 2x extender.

Well, strictly speaking an extender always reduces image quality, but the result is still much better than interpolation. This is a consistent finding.

Some notes about using the extender:
- If you try to interpolate instead of using an extender, you will also interpolate noise. With an extender - even if the resolution was equal to an image with no extender used, the end result will be cleaner because you don't have to crop and interpolate the original. The benefit of this depends on the ISO used, of course.
- using a 2x extender will lose 2 stops of light
- using the extender will also decrease hand-holdability by a factor of 2x....
... So, you end up with hand holdability of 3 stops less. This is where IS or a tripod / monopod / bracing will come in handy.

settings for the pics where, of course:
- exact same focus point
- MLU
- tripod
- several shots - sharpest selected

ps. click "original" size when viewing the images.