This shot shows how the Canon 400mm f/5.6 L lens can produce sharp images in low light despite the lack of image stabilization, using a monopod. This is a 100% crop of a picture I took on my tree-shaded back deck on a cloudy morning, with my Canon 20D and the 400/5.6 lens. Lens wide open, ISO 800. I was using my Bogen 684 monopod. This was a quick grab shot of a bird foraging, and moving every couple of seconds, so I wasn't able to be careful and use the best technique.

The feathers on the side of the bird's neck are reasonably sharp, so the blur of the bird's head is due to subject movement rather than camera shake. The point of focus was just behind the bird's bill, not on neck, and the lens doesn't front focus.

The picture was taken in RAW, converted with Breezebrowser, sharpness setting "normal." No other processing was applied.