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How do light meters work?


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#1 Tyler Leisher

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Posted 09 August 2008 - 09:51 PM

I'm not a cinematographer (Although I do love it), I'm a director trying to understand lighting and cinematography more... but one thing still baffles me.

What are light meters, what are they for, how do they work? Do you need them for digital video? High Definition Video? 16/35mm?

How should you use them?

I know I don't NEED to know this stuff, but I like to have an understand of everything in the film making process, so I can make better films more smoothly.
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#2 Adrian Sierkowski

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Posted 09 August 2008 - 11:35 PM

A light meter measures the amount of light falling on it and calculates the exposure to turn that quantity of light into medium gray given a set film speed. they are no necessary for digital video, though can be useful. It's a way of knowing that on X film stock with Y light on the subject, a lens setting of Z will properly expose the scene. . .
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#3 Ira Ratner

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Posted 13 August 2008 - 06:55 PM

Tyler, you say you're a director, and you don't "need" to know this stuff? With all due respect, how old are you?

I'm just an "a-hole" doing this as a hobby, but I know that a real director would HAVE to know this stuff.

Still film photography is based on just two simple concepts--light and surfaces. And the only way to expose it right is through proper lighting and metering.

Same thing with video and digital.

If you don't understand metering, how can you plan what you'll do for a particular shoot? Yeah, you'll get the shot, but with or without additional lighting will make a ton of difference in how it looks.
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#4 John-Erling Holmenes Fredriksen

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Posted 14 August 2008 - 02:04 AM

I'm just an "a-hole" doing this as a hobby, but I know that a real director would HAVE to know this stuff.


Even though a lot of directors are very into the visual and technical aspects of filmmaking (and they should, it's a big part of the movie experience), there are also directors who just don't care, and get by because they have a DP who covers for them. So blowing him off for not knowing might be a bit unfair.
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#5 David Auner aac

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Posted 14 August 2008 - 02:56 AM

I'm just an "a-hole" doing this as a hobby, but I know that a real director would HAVE to know this stuff.


No he would not. that's what cinematographers/DPs are for. A director needs to tell the story mainly by working with the actors to act the story on the one side and the DP on the other to make the images for the story. There are many directors who do know that kind of stuff, yes, but they actually don't need to! If you are a micro crew show (i.e. one or two people,) then things are very different of course.

Regards, Dave
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#6 Stephen Williams

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Posted 14 August 2008 - 03:05 AM

No he would not. that's what cinematographers/DPs are for. A director needs to tell the story mainly by working with the actors to act the story on the one side and the DP on the other to make the images for the story. There are many directors who do know that kind of stuff, yes, but they actually don't need to! If you are a micro crew show (i.e. one or two people,) then things are very different of course.

Regards, Dave


Hi Dave,

The problem directors are the ones who don't have a clue about this stuff but think the do! :lol:

Stephen
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#7 David Auner aac

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Posted 14 August 2008 - 03:24 AM

The problem directors are the ones who don't have a clue about this stuff but think the do! :lol:


Hi Stephen,

how true, how true. They usually need the largest amount of friendly pressure to keep them from making grave mistakes. "No problem, I know this effect in AFX, we can fix that in post!"

Yuck!

Regards, Dave
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#8 Ira Ratner

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Posted 14 August 2008 - 05:56 PM

I'm gonna cry foul and say no fair here:

We're talking about the simple concept of film/video sensitivity...aperature/shutter speed (where appropriate)...and lighting.

For 99% of productions, I can't believe the director isn't going to know what F16 means. Or 50 ASA. And that the two can't be used at midnight or indoors without additional lighting.
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#9 Chris Keth

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Posted 14 August 2008 - 06:52 PM

I'm gonna cry foul and say no fair here:

We're talking about the simple concept of film/video sensitivity...aperature/shutter speed (where appropriate)...and lighting.

For 99% of productions, I can't believe the director isn't going to know what F16 means. Or 50 ASA. And that the two can't be used at midnight or indoors without additional lighting.


You would be surprised. I would actually say that probably 75% of directors I have worked with or around have at least a basic knowledge of those things.
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#10 Adrian Sierkowski

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Posted 14 August 2008 - 07:06 PM

I've been lucky with about 50% knowing the basics (T film is inside film, for example) and maybe 25% of that knowing it pretty well (it takes an 85 to correct T to D). The other 50% generally just know the story and what they want to be conveyed in the images. In either case, so long as they're open to my input/advice from time to time, i'm 100% happy with them.
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#11 Chris Keth

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Posted 14 August 2008 - 07:14 PM

I've been lucky with about 50% knowing the basics (T film is inside film, for example) and maybe 25% of that knowing it pretty well (it takes an 85 to correct T to D). The other 50% generally just know the story and what they want to be conveyed in the images. In either case, so long as they're open to my input/advice from time to time, i'm 100% happy with them.


You've done well, then. My experience is that the really fun directors to work with are those who know that you have more knowledge and experience in photographing films than they do. That makes them respect you and your input. Even better directors tend to have some knowledge of photography. This allows them to make educated decisions while still respecting your input.

I have also worked with the opposite type of director who either knows a great deal about photography or thinks that they do. I've basically been told what lights to put where and exactly what to do with the camera. Those jobs were not fun (especially the director who only thought he knew what he was doing. I didn't even want my real name credited.) and I know now to try and avoid it in the future.

To the OP: The basics of a lightmeter were explained well up above. The tech of how they work wasn't. Most lightmeters work with a photovoltaic cell. That's a fancy name for a solar panel like you may see generating electricity. They use a small one with the idea that, if you know how much electricity the cell produces with a given intensity of sunlight, you can calculate the intensity of light for all other quantities of electricity produced. Combine that with a table of proper exposures for various speeds of film and you have the makings of a lightmeter. In the past the meter was just a voltmeter attached to the photovoltaic cell. It moved a needle that you could read a number of footcandles from. You could then use that footcandle number to figure out a shutter speed/fstop combination. Nowadays it's all programmed into the meter.
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#12 Adrian Sierkowski

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Posted 14 August 2008 - 07:21 PM

I have also worked with the opposite type of director who either knows a great deal about photography or thinks that they do. I've basically been told what lights to put where and exactly what to do with the camera. Those jobs were not fun (especially the director who only thought he knew what he was doing. I didn't even want my real name credited.) and I know now to try and avoid it in the future.


That sounds so familiar too though. But, yes, lately I've been very blessed by directors. . . but don't get me started on producers!


Also, back to meters, some of them even have "camera profiles," on them, though I'm still not 100% sure what that means. They're all special calculators. And just make you look so much cooler in your local starbucks line before going on a shoot.
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#13 Chris Keth

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Posted 14 August 2008 - 07:43 PM

That sounds so familiar too though. But, yes, lately I've been very blessed by directors. . . but don't get me started on producers!


Also, back to meters, some of them even have "camera profiles," on them, though I'm still not 100% sure what that means. They're all special calculators. And just make you look so much cooler in your local starbucks line before going on a shoot.


The camera profiles thing works on a characteristic curve of a particular camera. When you're in the mode that saves a bunch of readings, it will tell you when the contrast range goes outside the range of the film or video camera. I don't think it's a feature I would ever use because the camera profiles are based on some mystery settings, probably defaults. If you process differently or tweak camera settings, you would have to spend the time to make a custom profile. Some people might use them but for me it's too time consuming and something I wouldn't use anyway. I like my plain jane Minolta autometer VF.
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#14 Adrian Sierkowski

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Posted 14 August 2008 - 07:53 PM

Yeah I saw it in the manual for my sekonic. . .but, once it started talking about syncing with my computer. . .I skimmed ahead to more important things, like how to lock the wheel so I don't mistakenly change fps putting it into my pocket.
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#15 Tyler Leisher

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Posted 15 August 2008 - 06:34 AM

Thanks guys, this absolutely helps.

Ira, I understand the basics of lighting/camera movement/framing/blocking/aperture/etc... what I didn't understand is how light meters specifically work, what the light meter should read and whatnot. I don't know these things because I've never used one before, but in an attempt to learn more about the technical side of things I came here to ask the question. Even you should understand that you can't know everything all of the time, but that life is a non-stop education track. There's a reason I was asking, not to sound like a director, but to LEARN more to be a better director. :)
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