Strange water formation in long exposure

Started Jul 22, 2013 | Questions thread
MOD Dale Buhanan Veteran Member • Posts: 4,280
Re: Strange water formation in long exposure

ktownbill wrote:

PeterK wrote:

Well, here's my 2 cents:

#1: It is definitely one drop of water projected into the air at an angle, forming a classic parabolic projectile motion trajectory.

#2 Something is definitely flashing light on the droplet at even periodic intervals (the distance between the drops caught in the light display the characteristics of projectile motion, where the object travels greater distances near the ground, and smaller distances near the top of its trajectory)

#3 I doubt the full trip took the drop 2 seconds, for this simple reason:

a) from the top of its trajectory to the water's surface would take the droplet the exact same amount of time as from the water's surface to the top - they each take 1/2 the total time in flight (basic physics)

b) If the time to fall from the top of its trajectory is one second, the height would be 5 meters, or about 16 feet. Again, basic physics: all objects in free fall near the surface of the earth fall 5 meters in the first second.

c) as noted previously, it is hard to tell the exact scale, but I don't think that is a 16 ft high arc.

d) The exact time of its trajectory isn't really that relevant though.

#4 The big question is: what is causing the "strobe" effect?

- I don't think anyone has mentioned the second most obvious source of light in the frame, aside from the sun: REFLECTIONS from the WATER.

- Now, what might be causing a periodic reflection from the water?

>> The waterfall hitting some natural barrier at the base of the water that is periodically moved back and forth by the waterfall, or perhaps a pool of water in a rock that is periodically filled and emptied by the waterfall. The possibilities are endless, and I'm sure we could all imagine numerous other physical phenomena that will produce periodic motion at the base of a waterfall - in this case, periodic motion that results in the reflection of the sun's rays into the air where that drop happened to be thrown into the air.

Simple harmonic motion at the base of a waterfall seems a much more probable event than a strobe assist beam lighting that drop at such a large distance - to me, anyway.

Rather than just guessing and hypothesizing why don't you compare the frequency of the water-drops to the frequency of the AF-Assist beam and see if they match?  You aren't curious

Once the camera had focused and took this shot, there is no further AF assist.  That all happens before AF is locked and the camera will fire. So there is no way the AF assist would be active during the shot -- unless it came from a second camera.  But then the whole waterfall would have the strobe effect.  It has to be something else.

My guess would be sunlight flashes reflected up from water ripples on the pond.  That would be intense enough, directional enough, close enough, and you can get fairly fast ripple play.  Whether that is really the cause I don't know.  But this is a strange anomoly to be sure. I've never seen anything quite like it.

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kind regards

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