[Jeremy]

Hi folks,
Just wondering if anyone has succeeded in getting optically decent results using any 2x TC on the Sigma 500mm f/4.5? I`ve used the Sigma 2x, but been quite disappointed with the image quality. I know some get excellent results with the Canon 500mm f/4 with a 2x TC (and even with stacked converters). I`ve had good results using the Kenko Pro 1.4x TC, so was wondering if the Kenko Pro 2x might give better results. Anyone used this combo (Kenko Pro 2x plus Sigma 500mm f/4.5)?
Thanks for any comments.

[postcardcv]

I've got a 2x tc and a Sigma 500 f4.5, I posted a thread last year to show my test shots with the set up - http://www.birdforum.net/showthread.php?t=57067

To be honest I don't use the 2x tc very often as I am not great at manual focusing, so I prefer to use the lens with a 1.4x and retain AF. With the 2x tc I find I only get decent shots when the bird is big in the frame (which is when you don't really need it), but I guess this is because MF is easier with a big subject.