Saturday, November 11, 2006

time and chance





4 comments:

Rahul said...

Nice strobe effect. The lamp looks more like a mercury lamp to me, and whether mercury or fluorescent, I'd have thought that the phosphor coating would remove the 100hz flicker that you mention in an earlier post... You could try just waggling your finger in front of that light: if you do it in front of a TV (which is about 24 Hz I think) your finger seems to break up into several fingers, but with the fluorescent lamp in my room it's just a blur. The tip of my finger probably moves as fast as an insect when I do that.

Could the strobe effect be an artefact of the digital camera, if you're using one?

Natasha said...

Yes, now that you mention it, they are probably mercury lamps. I'm not sure though.

Well, the other shots of motion with the digital camera don't produce this effect, eg the diwali crackers (where thing would be moving at faster speeds, or the star streaks in the Hampi pictures)

It may have to do with the flight pattern of the insects? If you look closely you'll see the body of the insect isn't strobed (I'll look closely at the originals too). Maybe the wings reflect enough light towards the camera only in certain positions, giving it a stroboscopic effect?

I know that sound from insect wings (bat sound fr echolocation) works somewhat similarly. There is a peak of sound reflection hence echo in the wing flap cycle. Maybe something similar here?

In fact the peak in sound is apparently distinct enough that bats can identify species based on it!

Rahul said...

Yes, it could be the wings reflecting selectively. I can't make out whether the bodies are blurred or merely overlapped, but the wings do all seem to be in the same "position", and it's unlikely the frequency of an external light source matches the wings'.

Interesting...

Natasha said...

hey, i looked at the pictures carefully. You can see the body reasonably continuously constantly exposed throughout the path. The wings themselves light up best at certain points. But you can actually see faint traces of the rest of the wing motion between these points.

Wing beat frequency is usually around 30-50 Hz....