Something worth mentioning about the new Canon teles: IS mode 3.

Everyone knows about the two traditional IS modes on Canon lenses. Mode 1 is the standard mode for pretty much everything. Mode 2 is for panning, apparently. I have to confess that in more than a decade of owning IS lenses, I've never found a reason to use it. Perhaps if I did motorsport things would be different.

So I paid no particular attention to the new IS mode 3 at when I decided to upgrade my 100-400 to a Mark II, but having tried it out I reckon it is a major bonus. Essentially, mode 3 is the same as normal mode 1 except that it doesn't start until immediately before the shutter actuates. So you don't see it in the viewfinder.

This is good for two reasons:

(a) It is significantly easier to track moving objects (such as birds in flight) because you are reacting directly to the movement of the object rather than to the apparent movement of the object as shown to you by the stabilised image in the viewfinder. It's like the difference between driving an old car with sloppy steering that wanders around the straight ahead and a new one that goes where you point it.

(b) You can hand-hold better with static subjects. Because you can now see exactly where you are pointing the lens (instead of where you are pointing it plus or minus a random amount contributed by the IS system trying to compensate for your movements), you get immediate feedback on how steadily you are holding it, and on which direction you should be adjusting your aim. I rate this difference alone as worth at least a stop, possibly two. And because I can hold the lens steadier, the IS system has less work to do, meaning sharper pictures become possible at lower shutter speeds.

Of course, you can still use mode 1 if you prefer, but why would you? Mode 3 is brilliant!