- Looking at the 2nd shot, the source video is 20 fps and the object is in view for a total of 19 frames. Crossing a distance of about 8 feet. ... gives an estimated speed of 5.7 mph
- I can't find any examples of motion blur, it seems to have a very fast shutter speed.
Both MediaInfo and iMovie give 68 frames at 30 fps for the 2nd clip, 28 of which (12 through 39) show the object, for a total duration of about 28/68 x 2.272 sec = 0.94 sec. That equals about 1/30 sec max per frame. But just based on the estimated length of the trajectory as derived from the size of the tube frame in the image and the time taken to traverse it, my number (5.83 mph) agrees well with your speed estimate.
However, the actual shutter speed (~ exposure time per frame) is critical. The object only 'moves' in 18 of the 28 frames it's visible, during which time it covers about 8 feet. That makes its apparent size a bit over 5 inch long (8 ft/18), and that seems to be about right compared to the (~ 2 inch?) tubing diameter of the swing set frame. If we take the minimally 3 full wing beats into account that appear to be visible in my interpretation of the object, the actual length would be at most something like 1.7 inch.
At a speed of about 5.7 mph (or about 100 inch/sec) the object moves for a distance of its apparent 5 inch length during an exposure time of about 1/20 sec. If its size is actually less than 5 inch, its apparent length should decrease at exposure times smaller than 1/20 sec. If, as I postulated, its actual length is indeed about 1/3 of that apparent 5 inch, the latter length should decrease to 1.7 inch at an exposure time of 1/60 sec, and remain stable at even shorter exposure times.
The maximum exposure time at 30 fps is 33.3 msec (1/30), or 50 msec (1/20 sec) at 20 fps. The actual exposure times will be less than these maximum values, say 1/40 sec or less at 30fps. If true, it means that you're probably right after all: at 1/40 sec the apparent length should be about half the 5 inch calculated above.
I'm sorry, but now I really need that drink you just earned...
