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Light Meters


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#1 Jase Ryan

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Posted 03 March 2008 - 06:36 PM

I was talking with a Gaffer on set the other day and when I mentioned that I thought a light meter was made to show the amount of light that would reflect of someone he laughed and walked away. SO, clearly I have the wrong idea here.

Can someone explain what and how the light meter reads light and at what intensity? I know it's 18% grey, but isn't that what they say is close to what caucasian people reflect?

And then can you further explain the grey card and what it does to shoot some at the beginning of a roll?

Thanks,

Jase
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#2 Adrian Sierkowski

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Posted 03 March 2008 - 06:41 PM

An incident light meter shows you 18% grey or zone V, middle grey. Caucasian skin is zone VI, generally.
The grey card at the begining of the roll is a reference for the colorist, something he can adjust to (i.e. it's green! so they add in magenta to make the grey grey)

Light meters do measure the amount of light falling wherever it's positions (incident meter) and show you the F stop required to expose for 18% grey zone V. From there you can augment your exposure for your desired result. At least that's how I learned it.
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#3 Michael Collier

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Posted 03 March 2008 - 08:03 PM

Its there to give you an idea of 'normal' exposure. if you light to key then something dark under that light will read normaly dark. If its bright it will read normaly bright. skin tones (of any complexion) should read normaly exposed if its lit to key.

Its really more of a referance mark to show how over or under key the light falling on a given subject is. If your at key then a grey card should give you a mid-grey density on the negative. There is a lot of subjectivity to 'normal' exposure however, so its more of a guide than any magic bullet tool that guarantees perfect lighting. Light everything to key and it won't look very good, in most cases.
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#4 Drew Hoffman

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Posted 10 March 2008 - 12:51 PM

I mostly think it's unfortunate that he laughed and walked away. Even if there was a more pressing manner, clearly he thought there was a better explanation and even taking 10 or 15 minutes at lunch would have been enough to cover some basics. Maybe its just me... but if you feel that somebody has the wrong information, they have at least a pseudo responsibility to provide the "right" information. I know I wouldn't know half of what I do if it weren't for the people who were good enough to share some of the knowledge that they've amassed over the years. I'm not saying that the steady cam operator (or whoever) should sit down, explain and breakdown everything that goes into being good with a steady cam. That's a specialty they've spent a lot of time (and probably a lot of money) learning. I'm just saying that films by their very nature are a collaborative process, not being willing to help others along is counter-intuitive and counter-productive... that's just my opinion and I digress quite a bit.



There are two types of light meters available. Incident and reflective meters. Incident meters read the amount of light falling on them, reflective meters read the light that is being reflected from the surface the meter is pointed at.

Reflective meters can be deceiving, they're not smart and they don't know what they're looking at. All they know is how to expose what they're looking at to look like 18% gray. If you take a reflective reading off of a white wall and expose for what it tells you, that wall is going to look middle gray. A gray card is perfect to use with a reflective meter, especially when you're starting new and don't completely understand how to place your exposure. Hell, I've spent an entire semester classes devoted entirely to the zone system, spot meters and learning how to place your exposure... and there are still many many many things I have left to learn.

When you have enough experience and knowledge, you can light the entire scene using your reflective meter. In the mean time, an incident meter is taken at the subject and is a good way to determine where you want to set your exposure. A reflective (or spot meter, which is specialized reflective meter that has a very narrow area of reading, usually 1 degree) is taken from the camera position and is good for reading the tonal range of your scene. You can then make sure that you're going to get detail where you want it and things are going to fall off to empty black or white where you want those.

Exposing a gray card and color chart at the beginning of the roll, as stated before, are used by the lab for the purpose of setting the right colors and intensities for your telecine or film print. Shooting them at the beginning of each roll helps establish consistency and helps ensure your colors and exposures will match from shot to shot during post. Coming from a still photography world, I like more density on my negative and will overexpose by at least a half stop to a full stop. Shooting a gray card for the lab makes sure that when the footage comes back that it's been printed correctly and doesn't look too bright.

This is also important if you want to change the color of your image specifically for a scene. Shooting a correct color chart at the beginning of the roll establishes what the colors are supposed to look like, then you're free to change them as you see fit. Without it (especially on a student or low budget production) the colorist has to guess what you want the colors to look like and may interpret a scene that's unusually blue as a mistake on your part and color it out... when that's what you were trying to do to begin with.

I think I got a little carried away there, I hope everything I said makes sense and is relevant to your question... if not, feel free to chastise me and I'll try to rephrase it.

Sorry.
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#5 Serge Teulon

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Posted 11 March 2008 - 12:14 PM

I mostly think it's unfortunate that he laughed and walked away. Even if there was a more pressing manner, clearly he thought there was a better explanation and even taking 10 or 15 minutes at lunch would have been enough to cover some basics. Maybe its just me... but if you feel that somebody has the wrong information, they have at least a pseudo responsibility to provide the "right" information. I know I wouldn't know half of what I do if it weren't for the people who were good enough to share some of the knowledge that they've amassed over the years. I'm not saying that the steady cam operator (or whoever) should sit down, explain and breakdown everything that goes into being good with a steady cam. That's a specialty they've spent a lot of time (and probably a lot of money) learning. I'm just saying that films by their very nature are a collaborative process, not being willing to help others along is counter-intuitive and counter-productive... that's just my opinion and I digress quite a bit.


I couldn't agree more Drew...the Gaffer who laughed at our fellow really needs to stop and look at himself!

Cheers
S
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Media Blackout - Custom Cables and AKS

Willys Widgets

Visual Products

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Abel Cine

Rig Wheels Passport

Paralinx LLC

CineTape

Tai Audio

The Slider

Wooden Camera

Aerial Filmworks

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