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
Versatile 70-200mm zoom range. 3.5-stop Image Stabilizer. USM autofocus. f/2.8-32 aperture range. 1.2m closest focus. Sealed against dust and moisture. 8-bladed diaphragm. Weight: 1480g, Dia x length: 88.8x199mm.
I recently got a hold of the Canon 2x Extender Version III. I primarily got it to pair with a Canon 70-200 f2.8 MkII to take it up to 400 mm, but I was interested in seeing how it worked with the Sigma. The following 2 images were taken on a tripod, about 50 yards out from an Osprey at rest in full sunlight.Then I sold the 70-200 2.8 and swapped it for a 70-200 f4 L IS. The newer f4 IS was much sharper than its older 2.8 cousin so I tried the 1.4x on that and was a little more impressed, though by that time I already had a 300mm f4 IS , so the 280mm reach of the 70-200 + 1.4 TC was a bit redundant.oPE4N.