In article ,
Bob Noel wrote:

In article kXwrg.62937$ZW3.47903@dukeread04,
"Jim Macklin" wrote:

Note the time delay is just a few seconds as the airplane
passes overhead and the wake rocks the boat, that was not a
telephoto lens but a real close pass.

I watched the scene several times last night. Note that the camera
pans down to see the boat "rocked" but by what? The bow wave
doesn't look close to the boat and it seems hard to figure out
the distant between the plane and the boat. Doesn't a long lens
put the background out of focus? (or did I get that backwards?)

Focus is a function of "depth of field" which is determined by the
apperature (f-stop) and shutter speed. The higher the f-stop (smaller
the apperature) the more the light rays which pass through the lense are
parallel, making the background more in focus.