You don't need to be shooting at 1/500, even for fast jets. a lot of the time 1/250 and even lower works just fine
I agree with you but I took as the starting point for the discussion Gord's recommendation for fast jets of between 1/500-1/1000 (which again I have no argument against if you can get it) & IS off.
However, a slower shutter speed should add to the argument for using IS/VR which obviously he acknowledges by saying that it's useful for props/helos (presumably due to lower subject speed & wish for prop/rotor blur).
Not going to argue with you but I suppose it is all down to varying technique.
well, it's not meant to be an argument but a discussion - I'm sure that technique, systems, personal preferences & local weather conditions all contribute.
Gord said:
I can't see how the in-camera systems will be better. Any lag will be down to the processing of the movement not the location of the IS system. You would also still be limited by not having it working in the diagonal axis.
In-lens IS/VR systems have an initial lag (usually around 1 sec) as they move the elements of the IS system & it settles. In-body sensor moving systems don't have this as they only move the sensor at the moment of shutter release*.
Then again at release I would imagine that the speed of movement of the sensor is of an order of magnitude faster than that of the elements of an IS lens as the moving mass is far lower.
So it's not a case of location of the IS but speed of response of the moving parts of the IS system.
Unfortunately I don't know enough about using IS in a diagonal axis situation on different systems (I'll take your word for Canon but they aren't the only ones with panning support) but I would imagine that it's possible for a system to process both axis (presumably 2 accelerometers) at once given enough processing power.
* there is at least 1 exception to this which is 1 of the 4/3 system cameras when used in LiveView mode - it's also an exception to the general rule that in-body IS doesn't show the effect of stabilisation on the image pre shutter release.