Here are some M with 2 1.4x TC and adapter paired with a 300mm f/4L IS. Taken at f/11, ISO 1600. M did a little shot gun initially when trying to focus, but locked on correctly after a second or two. I used my 580 ex II flash to light the birds since it was a rainy day. That might have been the reason the camera was hunting due to the assist light being blocked by the larger lens.