It is huge. I had fancied the 600 f4 but am glad I saw sense. At 3.8kg this thing sounds little heavier than the 3kg f4.5 version, but it aint. It is a bugger to transport when you are on a bike, but luckily fits in my new ruckack (20quid from the supermarket, yes I know but it is light and does the job and is camo coloured). But as the sparrow shot shows it is sharp wide open, even wth TC. Not as sharp as the legend, 300 2.8 IS, naked but works better with TCs as I only need a 1.4 now. Bokeh too is nicer. I think I am in love.
7D, 500 f4, 1600ISO, flash for fill