Strange water formation in long exposure

Started Jul 22, 2013 | Questions
Limburger
Limburger Veteran Member • Posts: 7,841
Re: Strange water formation in long exposure

Jeff's explanation so far is best imo.

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Cheers Mike

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Wei Kelun
Wei Kelun Contributing Member • Posts: 524
Re: Strange water formation in long exposure

TDR1 wrote:

Actually, ignore that, I'm pretty sure I've got that backwards. Water drops tend to take on more of a round sphere shape gradually.

I've noticed that if you look to the bottom left of the waterfall you can see other similar but less clear drops.

It looks like someone has used a flash with a multi/strobe type feature.

Not to be a pain, but water drops will look spherical only when removed from wind resistance, which in this case would be at the vertex of the parabola. Otherwise they end up looking lenticular.

I too see some drops in the lower left, as well as what look like isolated bubbles in the flow closest to the base of the nearest waterfall. There has got to be some kind of regular strobe effect occurring; the question is what's the source?

rjjr Forum Pro • Posts: 14,758
Makes me wonder

From my old electronic engineering days if there is some kind of timing/refresh signal on the sensor, converters or other circuitry that doesn't show up in short exposures but may show up in longer exposures under certain conditions or some sort of failure of a filter to prevent those signals from showing up in the output?

Wei Kelun
Wei Kelun Contributing Member • Posts: 524
Re: Makes me wonder

This is a fascinating thread. For all the world it looks like the light is being interrupted at an extremely regular 16 Hz. (I'm deducing that because the parabola is so regular, and because it looks like about a 2-second trip for the water droplet to make, although scale is ultimately hard to determine.)

The fact that the "flashing" seems to last for the same duration of the exposure is also very interesting.

Finally, there are bubbles and drops elsewhere that seem to be similarly frozen.

So what's going on? It can't be leaves shaking in the wind or some other natural strobe, since the rate is too high and the pattern too regular.

Any chance the strobing was caused by the on-board flash being used for AF-assist?

If there truly was no flash, then it's got to be some kind of interruption in the signal being recorded by the sensor, right?

ktownbill Senior Member • Posts: 2,191
Re: Makes me wonder

Wei Kelun wrote:

This is a fascinating thread. For all the world it looks like the light is being interrupted at an extremely regular 16 Hz. (I'm deducing that because the parabola is so regular, and because it looks like about a 2-second trip for the water droplet to make, although scale is ultimately hard to determine.)

The fact that the "flashing" seems to last for the same duration of the exposure is also very interesting.

Finally, there are bubbles and drops elsewhere that seem to be similarly frozen.

So what's going on? It can't be leaves shaking in the wind or some other natural strobe, since the rate is too high and the pattern too regular.

Any chance the strobing was caused by the on-board flash being used for AF-assist?

If there truly was no flash, then it's got to be some kind of interruption in the signal being recorded by the sensor, right?

I think you are on to something. The AF-assist is right around the frequency of the pattern. Excellent deduction on your part Wei Kelun!!

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Bill

photosen Veteran Member • Posts: 6,216
Re: Strange water formation in long exposure

Makes an already good photo... Fascinating!

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msowsun
msowsun Contributing Member • Posts: 663
Re: Strange water formation in long exposure

What ever it is, it looks like there is something similar to the left as well.

All I can think of is light reflecting off a flying insects wings.......

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dwalby Veteran Member • Posts: 5,895
Re: Strange water formation in long exposure

msowsun wrote:

What ever it is, it looks like there is something similar to the left as well.

All I can think of is light reflecting off a flying insects wings.......

you might be onto something there.  Perhaps a grasshopper jumped and flapped its wings and they reflected the light in certain orientations and not others.  I don't think its a flying insect so much because of the parabolic path that appears to start/end at the ground level.

Wei Kelun
Wei Kelun Contributing Member • Posts: 524
Re: Strange water formation in long exposure

Bugs can't explain the whole story, as there are also bubbles or droplets visible in the veil of the waterfall. If there wasn't some kind of strobing going on, these details would be completely smoothed out.

My bet is now on AF-assist pulses from the onboard flash.

TonyCo Regular Member • Posts: 270
Re: Strange water formation in long exposure

Jeff, I could buy into that theory except that the droplets (or whatever) are too evenly spaced.

PeterK Senior Member • Posts: 1,017
Re: Strange water formation in long exposure
3

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.

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Quirino2k Regular Member • Posts: 170
Re: Strange water formation in long exposure

I edited it so you guys can see it better... The droplets on the Right side are creating faint light trails, and at the end a gold looking dot at the end. I also discovered some more "frozen" drop in the water on the left side..witch i highlighted..

Also some of the leafs looks very blurred so maybe a gust of wind came through and made the tree leafs expose the drop just enough to freaze it.

I checked some of my own old photos of a cascading waterfall.. and it was a 5sec exposure but i could not find a frozen drop anywhere.

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ktownbill Senior Member • Posts: 2,191
Re: Strange water formation in long exposure

Wei Kelun wrote:

Bugs can't explain the whole story, as there are also bubbles or droplets visible in the veil of the waterfall. If there wasn't some kind of strobing going on, these details would be completely smoothed out.

My bet is now on AF-assist pulses from the onboard flash.

I'm convinced that Wei Kelun is correct regarding his theory on the illumination of the water droplet. If somebody has an oscilloscope they can easily measure the frequency of the af-assist strobe. That will put this thread to rest. I'm sure the numbers will match. I don't have my oscilloscope anymore or else I would do it.  Use a photo-transistor to trigger the scope.

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Bill

rockrose Regular Member • Posts: 140
Re: Strange water formation in long exposure

(Maybe it has been already said, but I did not read everything completely;) to me a quite logical explanation is there actually was a constant pattern of intermittent flying drops (maybe not all the time but for a few seconds). Fast flowing/falling water hitting irregular rockbottom (with moss) can cause almost every kind of unpredictable flow-pattern; you can even see it from the tap in the kitchen sometimes. I surely did see some strange flow patterns in waterfalls in the mountains. I count over 40 droplets in the arc in the picture, so every 1/20th second the flow produces a droplet bouncing and flying in the same way. It is very well possible it cannot be seen with the naked eye, as in classic film: faster than 1/18 sec we don't see it as individual drops anymore.

TDR1 Contributing Member • Posts: 540
Re: Strange water formation in long exposure

Wei Kelun wrote:

My bet is now on AF-assist pulses from the onboard flash.

Wouldn't the AF assist require that two cameras were in play at the time? One camera wouldn't fire the AF assist while the shutter is open unless it's faulty.

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TDR1 Contributing Member • Posts: 540
Re: Strange water formation in long exposure

rockrose wrote:

(Maybe it has been already said, but I did not read everything completely;) to me a quite logical explanation is there actually was a constant pattern of intermittent flying drops (maybe not all the time but for a few seconds). Fast flowing/falling water hitting irregular rockbottom (with moss) can cause almost every kind of unpredictable flow-pattern; you can even see it from the tap in the kitchen sometimes. I surely did see some strange flow patterns in waterfalls in the mountains. I count over 40 droplets in the arc in the picture, so every 1/20th second the flow produces a droplet bouncing and flying in the same way. It is very well possible it cannot be seen with the naked eye, as in classic film: faster than 1/18 sec we don't see it as individual drops anymore.

Don't forget it's a 2 second exposure. If they were all separate drops it doesn't solve the problem as to freeze the action to see single drops clearly the shutter speed would have to be fast, probably around 1/200 or faster.

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Leon Wittwer Forum Pro • Posts: 13,444
Re: Strange water formation in long exposure

Maybe the drop was oblong and rotating.  It might reflect light periodically simulating the blinking light on your aircraft.

Lonzo
Lonzo Regular Member • Posts: 157
Re: Strange water formation in long exposure

Hi,

without having read all the other replies.. this looks like a stroboscope effect - as you didn't use a flash it seems I figure that this could have been a single drop that was reflecting light in a periodical way while flying through a dark/shadowy area after bouncing off somewhere i.e. by a flickering branch/leaf somewhere in the pathway of the lightray during the exposure time - the scene seems to  be able to explain that

?

Best,Lonzo

WilbaW
WilbaW Forum Pro • Posts: 11,595
Re: Strange water formation in long exposure

TDR1 wrote:

Wei Kelun wrote:

My bet is now on AF-assist pulses from the onboard flash.

Wouldn't the AF assist require that two cameras were in play at the time? One camera wouldn't fire the AF assist while the shutter is open unless it's faulty.

Right. To get AF-assist you need to be in One-Shot, but if you're in One-Shot you can't open the shutter without focus confirmation, and AF-assist stops when focus is confirmed.

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AShimon Contributing Member • Posts: 797
Re: Strange water formation in long exposure

PeterK wrote:

#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.

I think PeterK gets the prize for the winning answer. Nice job, Photosleuth!

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