I'll be honest and say I've got no real science behind my preferences. Because I shoot hand-held with long lenses (typically the 500mm f/4 with a 1.4x on my 1D x; or lately, the 100-400mm with a 1.4x on my M6 Mk II), I simply aim for as high a shutter speed as I can achieve that will deal with whatever behaviour I can expect of the subject matter.Keith, what are your observations in relation to optimal shutter speed requirements for shooting stationary subjects with 90D?
I shoot with two 5D IV bodies. I found that my sweet spot is around 1/FLx1.5.
I do not shoot people slower than1/60 no matter what even at a UW angles.
e.g. T= 1/125s for FL=85mm IS =OFF, handheld.
"Stationary" objects for me are calm birds or other wildlife, so I need to cover off the prospect of them suddenly becoming not stationary.
I'm rarely below 1/800 then (which is less than the 1/FL x 1.5 rule) - that's where my M6 Mk II has been since I got it, even for the rugby game I shot with it - but I'm north of 1/1000 if I'm shooting subjects I know will be active. And this is as much to back up the IS in the lenses as it is any overt need to capture movement: good as the stabilisation is, I appreciate the comfort-blanket of a fast shutter speed, especially given how windy my part of the world tends to be.
Not much help to your described scenario, sorry!