There is at least one thread a month with someone asking what wildlife lens to get. In these threads I will without doubt mention how great a bargain the 400mm 5.6 is if you don't NEED image stabilization. I thought this evening I would prove that this $1500 CAD(new) lens is 90% of what my $5000 CAD (used) is. Both of the following were shot by me with the same 7D mkII and near the same settings as wide open as I could. First is the 400mm Settings 1/1600, F5.6 ISO 160 400 by Trevor Baldwin, on Flickr Next is the 500mm Settings 1/1600 F4 ISO 100 500 by Trevor Baldwin, on Flickr Now the sky behind the 500 shot is a little nicer since it had blue sky where the 400 had some cloud. Both of these were cropped to the exact same> I copies the crop info from one and pasted to the other. The only editing is exposure which was minor. Now to the comparison. Is the 500mm a little closer? Yes but not really by that much. Is the 500m sharper. Again yes but also again not by a huge margin. Where the main difference comes into play between these two lenses is when the light begins to fade. The 500mm can keep you shooting keepers well after the 400mm has been put away. This is the reason I recommend the 400mm so often instead of the zooms. It is just that good of a lens. It does take a bit of convincing to justify $3500 for the difference seen here.