Canon showed off the EF 600mm f/4L DO BR lens today at the Canon Expo in New York. It is substantially shorter than the current EF 600mm f/4L IS II USM lens thanks to the diffractive optics inside.
Under the glass was a full-on finalized mockup of what the lens should look like when it comes to market. You can see that it offers image stabilization with three stabilization modes and a focus preset and focus limiter.
Additionally, Canon has a working prototype on display mounted on a Canon 1D X.
This working model only had the glass inside with functional manual focus ring. There were no electronics or even an aperture control. So, everything you view through the camera is wide open at f/4.
It’s still pretty amazing how good it looks.
The above image should give you an idea of the scale of the lens compared to what we are used to seeing with a 600mm f/4 lens.
Below are a few more photos of the EF 600mm f/4L IS BR DO USM lens exhibit.