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Lighting for 1000fps


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#1 Juan Pablo Chapela

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Posted 16 April 2007 - 06:36 AM

Hi everyone...

In a couple of weeks I'll be shooting a scene with the Phantom HD camera from Vision Research at 1000 fps. In their web page the camera is rated ISO 600. I've read that tungsten lights flicker at more than 500 fps, so in order to avoid that I'd have to use lamps of more than 5k, or use them DC. Am I right?

Anyway... the shot we'll be doing is a "Madonna" (as in the italian virgin) walking in full shot with a wall in the background. I know it sounds weird to shoot that at 1000 fps, but it is for a video installation. Can anyone give me a rough idea of the amount of light I'll be needing? As always, we are a bit tight speaking of money.

Thanks,

J.P.
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#2 David Mullen ASC

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Posted 16 April 2007 - 10:51 AM

Well, that's about a 5 1/2 stop loss from shooting at 1000 fps, so 600 ASA becomes an effective 13 ASA or so on your meter.

Using the old rule that 100 ASA at f/2.8 = 100fc, therefore 12 ASA at f/2.8 = 800fc

So I'd guess you'd need about 800fc of light for an f/2.8.

Using mulitple big tungsten lights blended through a large diffusion frame may reduce any visible flicker problems.
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#3 Juan Pablo Chapela

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Posted 16 April 2007 - 11:18 AM

Well, that's about a 5 1/2 stop loss from shooting at 1000 fps, so 600 ASA becomes an effective 13 ASA or so on your meter.

Using the old rule that 100 ASA at f/2.8 = 100fc, therefore 12 ASA at f/2.8 = 800fc

So I'd guess you'd need about 800fc of light for an f/2.8.

Using mulitple big tungsten lights blended through a large diffusion frame may reduce any visible flicker problems.


Thanks David.

It hadn't ocurred to me that multiple lights blended through diffusion could reduce flicker. That's a good one.

About foot candles... I'm a bit rusty here. I guess I'm going to undust that Sekonic I have back there and do some tests... But I'm thinking at least 5k's for the background and something like that for the key as well. Is it true that the bigger the fixtures the less problems I'll have with flicker? Because I'd really want to give the character a nice rim light without a flicker in it!

Cheers,

J.P.
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#4 Chris Keth

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Posted 16 April 2007 - 11:30 AM

To get you started with the figuring I grabbed this from the ASC manual:

A 5k fresnel with a 10" lens will throw ~950 footcandles when it is flooded and 10 feet from the subject. The beam width at these settings is about 9 feet.

Using mulitple big tungsten lights blended through a large diffusion frame may reduce any visible flicker problems.


David, is this because it will be setting any flicker of individual lights out of phase with each other, or does the diffusion offer some sort of interference to that flicker?

I have to remember that trick for a rainy day.
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#5 Simon Miya

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Posted 16 April 2007 - 11:42 AM

Using mulitple big tungsten lights blended through a large diffusion frame may reduce any visible flicker problems.

Will this still work if all the lights are running on the same circuit/genny? Doesn't the flicker have something to do with the line frequency?
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#6 Mark Henderson

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Posted 16 April 2007 - 02:13 PM

If you are powering off a generator you may want to power your 110 volt lights off 3 seperate legs (1/3 red, 1/3 blue and 1/3 off black). For your 220 lights you can run them off (1/3 red and blue, 1/3 blue and black, 1/3 black and red). This will get them on separate phases for you so they are not all firing at once.

Also, you can shoot at multiples of 60. This will keep you in line with the hertz of the power lines.
1020 would be the closest exposure.

Thanks, Mark
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#7 Kevin Zanit

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Posted 16 April 2007 - 05:10 PM

I do a TON of shooting at a 1000fps. It seems obvious, but I constantly see people make the mistake of just not grasping how much light they really need.

I have heard the 600iso figure, I don't know if it is true or not, but I strongly recommended doing some testing before the shoot.

To light a small product shot in a close up at about 200iso at 24fps I end up using 4 or 5 10ks only a few feet from the subject.

With tungsten light, anything under 5k will flicker, and the smaller the filament, the worse the problem. 10 and 20ks are best suited to this type of work. If you have DC power, Dinos are very good for this.

Kevin Zanit
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#8 Chris Keth

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Posted 16 April 2007 - 11:22 PM

I do a TON of shooting at a 1000fps. It seems obvious, but I constantly see people make the mistake of just not grasping how much light they really need.

I have heard the 600iso figure, I don't know if it is true or not, but I strongly recommended doing some testing before the shoot.

To light a small product shot in a close up at about 200iso at 24fps I end up using 4 or 5 10ks only a few feet from the subject.

With tungsten light, anything under 5k will flicker, and the smaller the filament, the worse the problem. 10 and 20ks are best suited to this type of work. If you have DC power, Dinos are very good for this.

Kevin Zanit



That sounds like a ton of fun, Kevin. What kind of stuff do you normally do at those kinds of speeds?
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#9 Kevin Zanit

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Posted 17 April 2007 - 12:41 AM

It can be fun; it is always interesting to see something that only takes one second in real time stretched out for 35ish seconds.

I do a lot of table top type stuff (product shots), but I have seen or shot more random things in slow motion than I ever could begin to recount. From water to fire to someone getting punched in the face to trick pool shots . . .
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#10 Juan Pablo Chapela

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Posted 17 April 2007 - 03:51 AM

Also, you can shoot at multiples of 60. This will keep you in line with the hertz of the power lines.
1020 would be the closest exposure.


Thanks Mark. I'll be shooting in Europe, so that'll make the lines 50hz, so in theory shooting 1000fps would be ok. Am I right?

Kevin... You are right... I'm gonna need a lot of light, it would be perfect, and necessary to do some tests. Unfortunately I won't have the camera, nor the lights availabe to make some tests. So it would be great to take advantage of experienced DOP's like you.

Cheers,

J.P.
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#11 Kevin Zanit

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Posted 17 April 2007 - 04:06 PM

At these high frame rats you can kind of through the convention of "safe" shooting speeds out the window. You not only see Hz rate type flicker but also "arc wander" (to steal a term from carbon arc days) with HMIs and fluctuations (for lack of a better word) in the filament of tungsten globes. The bigger the globe (i.e. 5k and up) the slower these fluctuations happen on the larger filament, and thus it is much less apparent.
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#12 timHealy

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Posted 17 April 2007 - 04:42 PM

I do a TON of shooting at a 1000fps. It seems obvious, but I constantly see people make the mistake of just not grasping how much light they really need.

I have heard the 600iso figure, I don't know if it is true or not, but I strongly recommended doing some testing before the shoot.

To light a small product shot in a close up at about 200iso at 24fps I end up using 4 or 5 10ks only a few feet from the subject.

With tungsten light, anything under 5k will flicker, and the smaller the filament, the worse the problem. 10 and 20ks are best suited to this type of work. If you have DC power, Dinos are very good for this.

Kevin Zanit



I friend of mine was the gaffer on a Disani commercial (Pepsi's bottled water) and I believed they used twelve 20k's for one shot with one lens of a 20 k pointed directly at the lens filling the frame. It was for a shot of the bottled water dropping into a tank of water seeing the air bubbles from the splash float around. I forget the details but the frame rate was very very high, as were the footcandles.

When doing this, my friend who does a lot of table top around fragile foods, typically uses a dimmer system. So the lights are only fully up for meter readings and actual shooting.

Best

Tim

PS I have always heard the use of putting lights on different phases referred to as a trick to shooting non safe off speed with HMIs. I have never heard of people doing it with tungsten. Have people really run into flicker issues when lights have been on one phase during high speed work? But when doing high speed photography there are other reasons to have lights on different phases like to keep the load balanced, especially when using a generator.
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#13 Kevin Zanit

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Posted 17 April 2007 - 07:31 PM

I have had flicker on 1k PAR globes and through testing anything smaller than a 5k. The multiple phases works at some speeds, but at a certain speed you are not seeing Hz rate flicker, but the actual arc of the HMI moving around looking like a flicker. You can get rid of this by putting it through some large diffusion frames, but you still need to deal with the flicker of any Hz rate issues as well.
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#14 Mark Henderson

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Posted 17 April 2007 - 08:41 PM

At 50hz, 1000 fps would be right. Sorry for my imperialism. God save the Queen!

I would never shoot this with HMIs. Too many problems you could encounter. In the United States, Rule of thumb with HMIs is that if you can divide the fps into 120 evenly (whole number, not a number and fraction) then it's a safe speed. Over 120 fps I guess as longs as it's in multiples of 120 such as 240, 360, 720, etc. it might be fine. Again, I'm speaking in USA numbers. In Europe with 50hz the fps should divide into 100 evenly.


(In the US there are 120 light pulses per second. In Europe, there are 100 light pulses per second.)
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#15 timHealy

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Posted 20 April 2007 - 09:47 PM

I would never shoot this with HMIs. Too many problems you could encounter.


I agree completely

Tim

Edited by timHealy, 20 April 2007 - 09:48 PM.

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#16 Jeff Webster

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Posted 01 May 2007 - 04:28 PM

4 or 5 10ks only a few feet from the subject.


I'm guessing you're not doing this for facial CU's. Get a little hot maybe?
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#17 Kevin Zanit

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Posted 01 May 2007 - 04:36 PM

I need to do it for anything that should be exposed at a 1000fps. Sometimes that is a face or person, those times are times it sucks to be an actor.
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#18 Chris Keth

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Posted 01 May 2007 - 04:44 PM

I need to do it for anything that should be exposed at a 1000fps. Sometimes that is a face or person, those times are times it sucks to be an actor.


They can just pretend they're acting in the golden age of three strip technicolor process.
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#19 Kim Sargenius

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Posted 14 May 2007 - 07:03 PM

It hadn't ocurred to me that multiple lights blended through diffusion could reduce flicker. That's a good one.



It will help further as well if you can keep your lights on different legs / phases.



cheers,

Kim
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#20 Kim Sargenius

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Posted 14 May 2007 - 07:11 PM

Errrrm - I feel like I'm about to ask the dumb question here; but no-one's thinking strobes????



Kim
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