Not a good test of IS. The point of IS is that it's designed to stabilize a moving camera. The IS in the EF 100-400mm is tripod-sensing, meaning if the camera is very still (as it would be on a good tripod, or sitting on your table), the lens actually turns the IS system OFF.


What you want to do to test IS is take a picture of something with IS off at a shutter speed which you can (barely) hand-hold the lens, e.g. at 400mm and 1/500s, and take a picture. Then, adjust your ISO setting so your shutter speed is 2 stops slower (1/125s in this example) and take another picture - it should be significantly blurry. Then, turn IS on and take the same picture. If it's as sharp (or nearly so) as the picture at 1/500s, then your IS is working as it should.