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meter/lights question


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#1 Pawel Saladziak

Pawel Saladziak
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Posted 22 August 2006 - 09:56 AM

Hi all.
First of all I'd like to say what a great place this forum is for sharing knowledge.

I'm preparing to my first shooting. I want to shoot for slo-motion takes. I have Pentaflex 16 that will run at 96 fps - and that gives me 4 times slower motion when played normally.
The subject is going to be stuff like a falling orange, ice cubes, water drops etc... All shots on the blue screen.
I have bought recently a 16mm Kodak Vision 500 stock for this shooting. Tungsten ballanced. I have two 500W flood lights, that gives 3000k light. I want to shoot a few differend fps speeds, for most of the speeds and shutter angles I have time exposition chart on pentaflex camera. Last thing I need now Is a lightmeter.

So my question is:
1: can you advice me some cheap secondhand cine lightmeter to spot on ebay?
2. is 3000k light ok for shooting on the stock I mentioned above for further keying in postproduction?

regards
Pawel
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#2 Michael Morlan

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Posted 24 August 2006 - 10:26 AM

Hi Pawel,

One bit of data is missing from your question: How much light do your flood lights deliver at different distances? It is the comparison of illumination (measured in footcandle or lux) delivered to your subject and your film's ASA rating that determine whether you can hit an F-stop available on your camera's lens.

At first blush, I suspect that two 500w work lights will be insufficient to sufficiently expose 500ASA film at 96fps (192/sec exposure @ 180deg shutter.) Perhaps if you have them only three feet from the subject. ;) And that doesn't account for any creative use of diffusion you might include in your shoot.

Take a look at my online article "Choosing the Right Light." It discusses how to match light fixtures to recording media (including film emulsions and video camera chip-sets) by comparing manufacturer illumination tables, readily available on the net.

http://michael-morla...ing_a_light.htm

You will note that the article addresses the use of cine lights which come with footcandle tables from the manufacturer. Since you are using non-cine lights, you will have to determine their light output with the help of a lightmeter. To do so, set the meter to a footcandle (or lux) scale and take readings of the light from various useful distances (5', 10', 25', etc.) Be sure the light is projecting without any bounce from other surfaces like walls and ceilings. It's probably best to do this at night, outdoors.

Regarding your bluescreen shoot: You probably need more lights than just two 500w work lights. You want a sufficient amount of light to evenly illuminate your bluescreen to your desired f-stop as well as lights creatively illuminating your foreground subjects. Sometimes you can do both with the same lights but the flat-lit nature of the bluescreen prevents you from lighting your foreground with anything but flat lighting.

Regarding your color temperature question: I'm presuming you are doing a tele-cine or other form of transfer to the digital video domain. Today's chroma-keyers are pretty forgiving regarding the accuracy of your blue (or green for video) background. If your blue is a bit warm, the keyer should be able to manage it as long as your subjects don't approach that hue too closely. Note that your foreground subjects will also be cast a bit on the warm side. Perhaps an 1/8CTB gel on your lights would bring them closer to the film's ideal tungsten balance (along with the reduction in light such gels create.)

Hope that helps.
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#3 Kristy Tully

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Posted 01 September 2006 - 03:47 PM

Hi Pawel,

My first light meter in film school was the sekonic light meter. It is easy to use, and probably really cheap on ebay. Ideally with blue or green screen you use a spot meter, but I've shot them with just an incident meter before.

Shooting at 96fps you will need to compensate your lens by 2 full stops from 24 fps. So you will need to light your greenscreen for that. Seems like you'd be smart to have at least one other light in your arsenal so you can use your 2 500w light s to cross light your blue screen. That way you can have your objects far enough away from the screen that you won't have to worry about the blue reflecting onto you objects in the darker parts....and you can have your 500w lights close enough to give you enough stops, being careful that you dont put them so close that you get hot spts.


The 3000k light will be fine for 7218. I'd make sure my key light (the additional light you should get to light your subject) is also in that range and shoot a color chart or grey scale. Even if you just get a one light and not a supervised session that will give the timer a reference to balance the light correctly. I personnally wouldn't use any gels for fear of taking away more stop away. You're probably on the low side of the light scale as is.

Good luck
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Ritter Battery

CineLab

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Visual Products

Tai Audio

Rig Wheels Passport

Media Blackout - Custom Cables and AKS

Broadcast Solutions Inc

FJS International, LLC

rebotnix Technologies

Glidecam

Willys Widgets

Wooden Camera

Metropolis Post

Paralinx LLC