Flash Duration

Started Dec 2, 2007 | Discussions
RW Davis
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Flash Duration
Dec 2, 2007

I've been asked by a shotgun manufacturer how difficult it might be to photograph shot patterns from the side. They want to record the length of pattern from front to back.

So, I've done a little research and discovered sound triggers and laser triggers. I have Canon 580's, Quantum 5d's and Profoto studio lights.

I guess what I'm asking is what flash duration will record a speeding bullet? It seems to me I need something approaching 1/100,000 sec. duration. Does such a thing exist?

Bob

WFulton
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Re: Flash Duration
In reply to RW Davis, Dec 3, 2007

Have not done it, but I don't think 1/100,000 second is necessary. 1/20,000 second would be quite formidable to stop speeding bullets. To a degree, it depends on the camera distance (how closely you examine it) - if from 1 foot or 10 feet. The shotgun sounds like 10 feet. And 10 feet would hide more blur.

Nikon spec's their SB-800 flash this way;

1/1050 sec. at M1/1 (full) output (M means Manual flash)
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output

I would imagine the Canon was very similar, or most any camera speed flash. I am thinking you will not find anything faster, and should not need it. Lots of people use them to stop hummingbird wings at 1/20,000 second. Studio monolights are very much slower, not suitable for this.

The bullet would be pretty easy with an audio sensor and delay trigger, because we could get close (flash and camera can, humans should not). Dim surroundings, flash up close at 1/32 power. Open shutter manually in Bulb, fire gun, which triggers flash, close shutter. GN is 26 at 1/32 power and 50mm zoom, which is f/11 at 2.3 feet.... I wouldnt want the flash that close to a shotgun, unless near the muzzle. Some type of thick shield is no doubt in order.

I do milk drop splashes with a SB-800 and the trigger kits at http://www.hiviz.com
and it works very well.

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Hugowolf
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Re: Flash Duration
In reply to RW Davis, Dec 3, 2007

There are specialized strobes for this, but they are very expensive. Battery powered shoe mount strobes tend to have shorter durations than regular studio lights, especially when fired at reduced power. You can get extra power by using using several shoe type units all at reduced power.

A Canon 580ex has a flash duration of about 1/500 s (2 ms) full power, and almost halves at each halving of power. I haven't seen actual figures for a 580ex at 1/128 power, but you may be able to get down to 20 μs.

How good is your estimate of 1/100,000 s (10 μs)???

You would not be able to trigger a camera fast enough as this speed. You would have to use bulb.

Brian A.

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Ellis Vener
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Re: Flash Duration
In reply to RW Davis, Dec 3, 2007

Doctor Harold Edgarton at MIT was able to do stopmotion stills of speeding bullets with flash but he had some very specialized equipment. Google his name and do some research.

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RW Davis
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Re: Flash Duration
In reply to Ellis Vener, Dec 3, 2007

Thank you for the good replies. Guess it might be worth a try with shoe type flashes set at very low output. Now if I can just find someone to hold the camera while I shoot the gun...lol.

My 1/100,000 sec. calculation wasn't very scientific. I was just thinking if a shotgun round travels approx. 1,000 ft. per second, and a flash duration of 1/1,000 sec, then the little BB's will travel 1 ft. during the length of the flash. Flash duration of 1/10,000 sec, they travel .1 ft.,,,1/100,000 sec, they travel .01 ft. A rifle bullet would be much faster, 3,000 fps up to 4,000 fps.

I'm going to have to keep investigating.

Thanks,

Bob

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RW Davis
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Re: Flash Duration
In reply to Ellis Vener, Dec 3, 2007

Ellis,

Thank you for the information. I'm very familiar with Dr Edgerton's work. As a coincidence, I have a close relative that knew him and now works for a company he helped found.

Bob

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WFulton
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Re: Flash Duration
In reply to RW Davis, Dec 3, 2007

RW Davis wrote:

My 1/100,000 sec. calculation wasn't very scientific. I was just
thinking if a shotgun round travels approx. 1,000 ft. per second, and
a flash duration of 1/1,000 sec, then the little BB's will travel 1
ft. during the length of the flash. Flash duration of 1/10,000 sec,
they travel .1 ft.,,,1/100,000 sec, they travel .01 ft. A rifle
bullet would be much faster, 3,000 fps up to 4,000 fps.

To measure the length of a shot gun pattern from front to back probably does not require 0.01 foot precision. Who would see that precision if viewed from several feet back?

But do not under estimate the camera speed flash.

Consider a Dremel grinder, rotating 30,000 RPM, with a disk that is one inch diameter. 3.14 inches circumference 30,000 times per second is 94,200 inches per second at the rim, or 7850 feet per second (faster than a speeding bullet).

See the third picture (last picture) at http://webs.lanset.com/rcochran/flash/hss.html

The subject there is unrelated but yet that picture exists. Note this is viewed not from ten feet, but possibly from as much as ten inches. Which is a close up view which greatly magnifies any motion. It is not about the shutter speed of course, it is about the speed of the flash.

Says it is a Sunpak 383 Super flash, which retails for $80 at B&H. No details were provided, but obviously it was up close and at lowest (fastest) power. I doubt you can get that close to the shotgun pellets, so the flash is slower, but also your eyesight is not as detailed at the greater distance.

I think the rifle bullet would be easy (up close, maybe 12 inches) but the shotgun seems much more problem. At least my own flash and camera are not available for this purpose.

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Yehuda Katz
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Bob,
In reply to RW Davis, Dec 3, 2007

Make your life easier and begin experimenting with an air rifle gun. Much-much safer and not ear deafening.

Yehuda

RW Davis wrote:

I've been asked by a shotgun manufacturer how difficult it might be
to photograph shot patterns from the side. They want to record the
length of pattern from front to back.

So, I've done a little research and discovered sound triggers and
laser triggers. I have Canon 580's, Quantum 5d's and Profoto studio
lights.

I guess what I'm asking is what flash duration will record a speeding
bullet? It seems to me I need something approaching 1/100,000 sec.
duration. Does such a thing exist?

Bob

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Dasher
Contributing MemberPosts: 787
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Re: Flash Duration
In reply to WFulton, Dec 3, 2007

You got lost in your math a little.. 30,000 RPM is 500 rev/s so 3.14* 500 12 = 130 ft/s

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Dasher
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Re: Flash Duration
In reply to RW Davis, Dec 3, 2007

Capturing the shot pattern might be easy might be hard. Did the manufacture specify how far from the muzzle they want to record the pattern.

The muzzle velocity of a shot gun is in the range of 1100 to 1300 ft/s or so. It might be possible to have a strobe trigger off of the light flash from firing the gun. Since the flash occurs after the projectile leaves the muzzle, the flash should be able to capture it.

A flash duration of 1/48000 would result in 0.03 inches of blur, #5 shot is about 0.12 inches in dia, so the blur is about 25 percent of the shot diameter. Not too bad, especially if you are looking at a group of shot and not a single shot.

If you need true stop action, you would need much faster strobe.

I think the tricky part will be if you need to delay the flash, then you will need some electronics to provide the necessary delay.

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WFulton
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Re: Flash Duration
In reply to Dasher, Dec 3, 2007

Dasher wrote:

You got lost in your math a little.. 30,000 RPM is 500 rev/s so 3.14* 500 12 = 130 ft/s

Right, RPM... thanks.

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Ed Halley
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"time machine"
In reply to Dasher, Dec 3, 2007

Other folks are suggesting using the muzzle blast or other ad-hoc way of arranging the time to fire the strobe.

You'll be more productive with an off-the-shelf trigger like the Time Machine product. You can trigger the system with sound or muzzle flash or (if stopping bullets not buckshot) the bullet itself can break a laserbeam. Then you can tune the number of microseconds delay from the time of trigger to the time of flash, so you don't have to keep repositioning the camera.

I don't even have one, and I don't work for them. I'm just suggesting this brand as a well-regarded example in the class of devices.

http://www.bmumford.com/photo/camctlr.html

As an aside, if you put a ruler "behind" the shotgun blast, at the same distance as the camera, then the ruler scale would be an easy-to-calculate 2:1 ratio. If the shot pattern midair covers 6" on the ruler, that's a 3" spread. You could even print a custom 2:1 ruler so the numbers measure up properly. Just remember that the distance from Camera-> Shot should match the Shot-> Ruler distance.

-- hide signature --

[ e d @ h a l l e y . c c ] http://www.halley.cc/pix/

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nc3
nc3
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Re: Flash Duration
In reply to RW Davis, Dec 4, 2007

Have a look at http://www.rit.edu/~andpph/exhibit-3.html - quite a way down the page for some examples of what the image might look like - especially with the smoke.

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ischyros
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Re: Flash Duration
In reply to nc3, Apr 30, 2008

I thing you can do better with an hi speed camera (20 000frame rate) and continous light. maybe borrow it somewhere.

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