Originally Posted by James Shadle You can do it - Stacked Converters. I tried this just for the heck of it and I was blown away. Nikon D700, Sigma 300-800mm @ 800mm. Kenko Pro 300 DG 2x stacked with a Kenko Pro 300 DG 1.4X = 2240mm ISO 800 1/320 @ F20, No VR -IS -VC -OS, just proper long lens technique.