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Simulating Rapid Flash Photography


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#1 Craig Knowles

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Posted 25 February 2007 - 01:16 AM

I've got a project coming up where I'd like to simulate a KO'd boxer being flash photographed by a barrage of photographers in a medium shot.

My first thought was to get a bunch of disposable cameras, but there are several drawbacks to this -- the recharge rate on these are very slow, and most importantly, the speed of the flash and almost instant decay may not even show up on film.

I know that for Raging Bull, Scorsese used an old style of flash bulbs which had a nice slow decay, but he mentioned that they were very expensive.

Scorsese used a somewhat similar technique in The Departed when showing dead bodies of which photographs had been taken -- one or more large, slow-decay flashes of some sort.

Any suggestions as to how I could (inexpensively) simulate a barrage of flash photography?

One thought I had would be to shoot at a quicker frame-rate -- something less than 24 fps -- and do a quick on/off of a couple of 1K or 2Ks.
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#2 Michael Nash

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Posted 25 February 2007 - 01:25 AM

Switching conventional movie lights on and off would be too slow for a convincing photo-flash effect at 24fps or higher. The filament is too slow to come to full brightness. And the larger the unit, the slower it is to come to full brightness.

I've usually used a combination of flash sources including disposables, digital cameras, rechargeable SLR flash units, and Data Flash units.
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#3 Nick Mulder

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Posted 25 February 2007 - 03:00 AM

My first thought was to get a bunch of disposable cameras, but there are several drawbacks to this -- the recharge rate on these are very slow, and most importantly, the speed of the flash and almost instant decay may not even show up on film.


As in they wont show up as the shutter was closed the time ? - its possible yep... I have a bin downstairs here filled with about 200 disposable camera flashes that i used for a similar sort of project - watch out, when charged the caps give quite a jolt (all that from a AAA battery!) -

You pretty much need exactly the circuit I made but have since lost the diagram - but in a nutshell:
  • You need to have a sync output from yer camera - if it doesnt have one (ie. it aint super-8 or some relatively rare 16mm) you can usually hack one together with a hall effect sensor operating off a 1:1 shaft (something that moves in 1:1 or some other ratio of the shutter)
  • Set this up with a comparator of some sort so that you get an electronic pulse that also in turn operates in sympathy with your shutter ...
  • Send this pulse into a 4017 decade counter (cheap as chips!) that will fan out the pulses in sequence at the fps ...
  • each of these outputs can control a flash via an SCR that will each flash when the shutter is open (as you set up the hall effect sensor in the right place) -
  • you would have to miss steps (frames) in the 4017 so as not to have constant lighting, or at least move the bulbs around a bit so the shadows fall differently ...
  • You'd also need to have more than 10 frames of flashes so you'd link a few 4017's together ...
  • the flashes only flash once with this set up (if you left it on until they recharged they'd go again) , no need to worry about recharge rates ...
easy! right ?

yeh, I know its probably a load of gibberish if electronics aint your thing - but maybe it'll give some hints to your old school nerd buddy who you can pay to make it for you

parts cost: around $20
watch out for epileptics

(you're not in New Zealand by any chance ? :lol: )

**********Edit**********
Like this badboy - but with SCR(or mosfet)/flashes instead of LED's and the hall effect sensor via an op-amp as the clock input ...

you get the picture from the diagrams there much better than my description...

Edited by Nick Mulder, 25 February 2007 - 03:01 AM.

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#4 Chris_Burket

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Posted 25 February 2007 - 04:21 AM

Why not use strobe lights at various rates? They have a bunch setup at the Oscars right now on Hollywood Blvd. I first saw them and thought they might be slaves setup for the the still photographers to give the stills a uniform appearance. But then I saw them flashing randomly today as they were setting up, and they didn't react to other flashes like slaves would. Makes me think they might be using them to augment that array of flashes look but I don't know for sure. But, I'm sure they could be used to that type of look....
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#5 Nick Mulder

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Posted 25 February 2007 - 05:28 AM

Why not use strobe lights at various rates?

You could but you end up with two possibilities that may or may not worry you:

The flashes all happen when the shutter is closed (unlikely but still possible) or
It ends up looking too much like 'strobes lights at various rates' (which is really the less of these worries)

and yep, these two issues seem to contradict each other but they are at each end of the scale of poopiness

With the system I proposed you can in essence sequence (program) the flashes frame by frame - no more luck involved, more work though !

Edited by Nick Mulder, 25 February 2007 - 05:32 AM.

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#6 Patrick Neary

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Posted 26 February 2007 - 12:31 PM

I've usually used a combination of flash sources including disposables, digital cameras, rechargeable SLR flash units, and Data Flash units.


Hi-

Where do you get your Data Flash units from, and are they comparable (in intensity, coverage, etc) to the smaller Lightning Strikes units?
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#7 chris kempinski

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Posted 26 February 2007 - 07:39 PM

Data flashers are great but be worned,
They don't have a great lifespan, meaning, if your shot is longer than
perhaps 10 seconds the gas becomes too hot and you have a hot strike
situation, they stop working, and take a considerable amout of time to cool
down. The output is great though, we just shot a commercial for a remote control
toy, built a grand stand with 108 zenon flash bulbs on a nail board to fake a
stadium of people and used the data flashers for the photo flashes. We shot at
150 fps with a snorkle lens (minimum stop of a T8), we needed enough light in studio
to achieve an f22 at a 50ASA.
Wew, that was a tough show, it was all like that. High speed and an 8 stop.

Cheers
Chris
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#8 Richard Andrewski

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Posted 26 February 2007 - 10:07 PM

Couldn't you just do this with an NLE plugin of some kind? Wouldn't that be a lot easier? I'm not near my Vegas machine now but it seems like I remember a plugin of this sort that would allow a flash effect in the video.
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#9 Nick Mulder

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Posted 26 February 2007 - 10:20 PM

Couldn't you just do this with an NLE plugin of some kind? Wouldn't that be a lot easier?

No where near as fun - and you wouldn't have the shadows a real light would cast ...

Not to mention this is a cinematography forum :huh:

but yes it might be easier
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#10 Michael Nash

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Posted 26 February 2007 - 10:59 PM

Hi-

Where do you get your Data Flash units from, and are they comparable (in intensity, coverage, etc) to the smaller Lightning Strikes units?



I used them on a feature I gaffed where production located them for me (somewhere here in LA). Sorry I can't say exactly where it was.

I've got pretty limited experience with lightning strikes units, so I don't know all the photometrics. The nice thing about data flash units though is that you can get multiple effects from one set of heads and the controller. You can set the heads to fire simultaneously (positioned in different places if you like), or create a pattern amongst the heads that suits your purpose. On my feature for example, we got them for the express purpose of simulating flash photography at a few press conferences, but ended up using them in other applications like simulating aviation lights during a poor-man's-process helicopter sequence.

Yes they do get hot and have to cool off between uses in some setups. Just plan around that. For a scene such as a boxer getting ko'd, you'd probably have enough time between takes.

Regarding post effects; I've done that as a supplement to real flashes, but it doesn't quite replace the real thing. It can be a nice embellishment to flashes caught in camera, though.
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#11 Bobby Shore

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Posted 27 February 2007 - 01:04 AM

[quote name='Michael Nash' date='Feb 26 2007, 08:59 PM' post='157444']
I used them on a feature I gaffed where production located them for me (somewhere here in LA). Sorry I can't say exactly where it was.


check out Acey/Decey Lighting. They have Data flashes at pretty good prices. There's two types of controllers though: basically, a really complicated one and a not so complicated one. For the effect your going for (boxing ring KO), the simple controller with 3 or 4 data flashers would probably work fine. Make sure you set aside some time to play around with the units and the controller so you can set a pattern that works (i.e that can mimic the randomness of flash bulbs firing).

You can choose flash hundreds of flash patterns and the vary the intensity/rate at which they fire. Again, be careful about going with a high intensity as the units need a bit of time to cool off if they overheat. Just mess around with it till your happy.

As for the comparison to the smaller lightning strikes, these units don't have the same output at all (they still can generate a ton of light though), but for what you want to do, it sounds like you can have the units relatively close to the action.
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#12 Craig Knowles

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Posted 27 February 2007 - 11:37 AM

Couldn't you just do this with an NLE plugin of some kind? Wouldn't that be a lot easier? I'm not near my Vegas machine now but it seems like I remember a plugin of this sort that would allow a flash effect in the video.


I'm sure it's possible, but it wouldn't look real. Consider a boxer, lying KO'd on the mat, being photographed by a 360-degree circle of photographers. With each flash, the three-dimensional lighting/shadow patterns will change dramatically all around the boxer -- lighting one side, another, the back, the front, creating sillhouttes, over exposure, areas of darkness, illuminating the background, the ropes -- randomly dependant on the orientation and direction the flash comes from.

Not the same effect as what you could get with a plugin at all.
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#13 Jonathan Bowerbank

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Posted 27 February 2007 - 01:01 PM

Maybe you could try a simple strobe light, like the kind you find for cheap at party supply stores?

They usually have adjustable speeds and might be what you're looking for.
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#14 Nick Mulder

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Posted 27 February 2007 - 02:50 PM

Maybe you could try a simple strobe light, like the kind you find for cheap at party supply stores?

They usually have adjustable speeds and might be what you're looking for.

See post#5 ;)
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#15 Richard Andrewski

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Posted 28 February 2007 - 01:30 AM

Haha, optical FX loses out to practical FX...
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#16 Michael Rizzi

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Posted 26 March 2007 - 10:04 PM

Hey,

Open up this thread again...

I have a related question to lighting with strobes. I'm wondering if anyone knows the output of those party store strobe lights. I'll be shooting 7218 with super speeds. The shot is low angle, tracking back on dolly, talent rapping into the wide angle the lens...I know what you're thinking...but we're going for that cliché hip hop video look. On the left and right side of the talent and the track I want a row of strobes all flashing at different speeds. Do you think 10 or so store bought strobes on each side about 2-3 feet apart would give me enough poop? Ideally I would like to be 2 to 3 stops over, and I will most likely be overcranking, like 48fps. And I'll be using some fill as well.

Any suggestions as where to get them, and/or more powerful lights if neccessary?

Thanks,

Rizzi
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#17 Nick Mulder

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Posted 26 March 2007 - 10:18 PM

The fps is redundant unless you have other lights going constantly ...

Only way to be sure is to get a flash meter make a little circuit that will trigger your party strobes and check the exposure...

X-sync on a camera was just a mechanical connection made by the movement of the shutter in the good ol' days - but newer electronic cameras and flash meters achieve this with an SCR or Transistor type cct - problem is most strobes are looking for a voltage pulse, not just a sudden reduction in resistance that X-sync does - you'll have to look up the specs on the strobe and nut that one out for yourself... I'd attempt to make a quick sketch of what I 'd do but can claim zero responsibility if you fry your light meter or the strobe (unlikely but ...)

This is assuming you have some sort of sync or pulse output timed with your shutter ?
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