First I should say that that trying to figure out speed based on fps is probably going to be a waste of time since you don't know distance from camera nor frames per second. But that said, I believe it to be a bat.
Interesting on both counts, but I happen to disagree with your conclusion. While I concurred with the problem the unknown distance poses for calculating speed, I'd like to point out that the clip offers other measuring options. To wit:
1. The 'quasi' object in the mystery clip moves
at least at about the speed of its apparent length per frame or 100msec. If its trajectory is not perpendicular to the camera direction, the object's speed is higher.
2. There are what looks like 3 up and 2-3 down (wing) movements visible per frame, based on the changeover points between up-stroke and down-stroke. Because the vertical wing speed is zero at these transition points, they appear more clearly at the top and bottom of the object (see frame #2).
3. If (2) is correct, that would suggest that the animal is 2-3 times smaller than it's apparent length, and that one up or down stroke of the wing takes about 15-20msec (100msec/5-6 strokes), or 50-65Hz. A full wing beat (one up + one down stroke) would then take 30-40 msec, or 25-33Hz, easily within range of insects (
approx. 5-1000 Hz).
4. As
bat wing beat frequency tends to range between 5 and 10Hz (200-100msec/beat), this appears to exclude a bat as the mystery object. Finally, given the relative size of the object within the frames, the smaller the actual size of the object, the smaller its distance to the camera must have been.
Comment?
