How to properly use a Light Meter

Donald Harvey

Donald Harvey

Active member
Can some one give me a lesson on how to properly use a Light Meter or Exposure Meter?

How to use it?

What are it's uses? (no jokes, I know that's a "here's your Sign" response)

And any other tips tricks, or advice when using the device!

Thanks for the help

DH
 
Blade Borge said:
This article really opened my eyes, http://www.cineobscure.com/dynamic-range-and-lighting-for-film/
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You know, I saw that article long ago and it's bugged me ever since.

Your light meter is reading the light, but it has no clue whats happening to that light after it goes through the cameras chip and through all it's funky things to give you a pretty picture.

For video, forget the light meter. You don't need it, it will only confuse you. Get a waveform monitor and you'll be able to see so much more than you ever would be able to with anything else. The only thing you're trying to do with a light meter is come out with a picture that has a full contrast range, that doesn't have anything that is over or underexposed. You can sort of approximate the dynamic range of your digital camera, but as soon as you change a setting, or a gamma curve, it's changed. It's different. Using a waveform monitor will show you your changes and how they affect the luminance values in your image. You'll know if you're now overexposing that white shirt after you change your gamma curve to high, where as with your light meter? Uhhh...you didn't test for that variable yet! Oh no!

Just realize that there are different tools for each format. I know some guys would look at me crazy if I tried to use a waveform monitor for film, so why can't I think you're crazy for trying to use a light meter for digital? On all the digital shows I've been on the DP is never out there with his meter. He's at the DIT station looking at the scopes and the monitor. That's just how it is.

As far as how to get a waveform monitor...you probably already have one. I got a 15 foot firewire cable and a laptop. I open up FCP and then I can use final cuts waveform monitor that they have. Sure, it isn't the best, but it works much better than me just guessing.

If you would like to get one to learn how to use it for film, I'd suggest getting a 35mm still camera and shooting stills with a handheld light meter. Better yet if you can get a meter with an incident and spot meter. I would also suggest reading Ansel Adam's book, "The Negative". That cleared up a lot of things for me with using the zone system, as well as learning how to use my meter.
 
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RyanT said:
Your light meter is reading the light, but it has no clue whats happening to that light after it goes through the cameras chip and through all it's funky things to give you a pretty picture.
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Exactly. I've been trying to explain this to people for about six years, but for some reason they just don't want to hear it.
 
RyanT said:
As far as how to get a waveform monitor...you probably already have one. I got a 15 foot firewire cable and a laptop. I open up FCP and then I can use final cuts waveform monitor that they have. Sure, it isn't the best, but it works much better than me just guessing.
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I have been trying to use my power book and FCP 6 as a waveform monitor but have not feed a live image into the program yet. Am I suppose to be in 720p/30p or another certain format?
 
"so why can't I think you're crazy for trying to use a light meter for digital?"

I'm too cheap to be dealing with film, but practicing my light meter with my 500iso digital camera has made me much more aware of such things as f/stops, footcandles, how exactly gels stop down a light and just the overall art of cinematography.

I don't adjust gamma/matrix/pedistal settings on my camera so I get pretty reliable results.

Nobody is saying the waveform isn't the final say so, but I love how my light meter gives me a nice ball park estimate for how much light I'll need before I even have to pull out the camera/wfm.
 
nickmicros said:
I have been trying to use my power book and FCP 6 as a waveform monitor but have not feed a live image into the program yet. Am I suppose to be in 720p/30p or another certain format?
Click to expand...

I think you have to be in 720p/24p, you can't be in 24pn
 
I use a light meter to make sure my dark areas only go as low as I want them to be.
If the dark areas are not lit, they will be grainy.
From there, I build the ratio of the key lights above the minimum i set my darks to be.

After it is all done, it will look too bright, but then in post, I bring it down to make the blacks solid, and the mid tones and highlights darker.

Post processing looks so much better if you have light to begin with.

I use a light meter mainly to set the difference in intensity one light has over another.
 
using light meter with digital

using light meter with digital

The answer to this question is a combination of what people have said.

A light meter is vital to determining accurate exposure of the subject. Whether using f-stops or footcandles (which come in handy when trying to read an average, and are much more useful when trying to communicate with a gaffer) a light meter will allow you to much more accurately determine exactly how much light is needed to give you your desired look. When you know your dynamic range, you'll be able to determine two really important things that a lot of people using digital overlook. How black are your blacks? (Or how black do you want them) How blown out are your highlights? With this knowledge, where is your key level and how does that compare to your shadows and highlights? In brief, using a light meter has the ability to give you a quantitative value of where exactly where every part of your shot falls.

Other perks of using a light meter
-It's portable
-You can measure while the camera is not there
-You can measure small parts of the frame much more accurately (especially if you have a spot meter)

The issue comes with how the light you are reading is read by the camera. This is where the waveform monitor comes into play. In most digital cameras, there are three big things that are going to affect how an image looks regardless of the settings (gamma, gain, any of that). Your f-stop, your fps, or your ISO. Since on a lot of digital cameras there is no setting for your ISO (ASA, EI, whatever), you have to determine the ISO of the camera using both your waveform monitor and a light meter.

BEFORE YOU BEGIN SHOOTING (as in don't get to set the first day and try to "do this real quick") hook up your camera to your waveform monitor and monitor. Set up a gray scale and light it how you should (flat, no hot spots, all that business). At this point, if you have a professional monitor then you can adjust the color, contrast, and gamma on the monitor, but if you don't, don't worry about it too much, just get the bars up and get it to look right. Once you are satisfied with the look switch back to the video feed of the gray scale and make sure it is filling the screen. Switch to your IRE which should read from -40 to 100, and set the correct stop on the camera so that you get your black levels at the appropriate spot by adjusting the stop on the camera. (For NTSC you want it about at 16).

Now you bring out the trusty ol' light meter. Read the gray scale. Your goal is to get the stop on the meter to match the stop the camera is set at. Get your fps set and don't touch it. The only thing you adjust is your ISO. Once your meter matches your camera stop, you have found the true ISO of your camera. The biggest thing to mind is that ISO can vary from camera to camera even if it is the same make and model, but once you have the ISO of a camera, it shouldn't ever change (but if for some reason, you get a different camera, say you shoot pickups and re rent from a camera house, you need to re do this process). Now that you have your ISO, you can take readins from your light meter that actually mean something. If the reading seems way off, you probably have not flipped the terminator switch which will show up on your waveform when it is way out of the bounds. (The terminator will either be a little switch on your waveform monitor or an option in the program you are using on your laptop).

With this process done, you have gained two valuable things: a way to qualitatively and quantitatively measure what is on screen. Your light meter will tell you what each light source is giving you, and your monitor will tell you how that corresponds visually.

The important thing to remember is that once you have all this information, you have to assess not only what it means, but also how the light you've read feels. A lot of times, you can read a scene, expose it perfectly and be dissappointed in how it turns out.

For example, a person comes out of a cave after being stuck for a week and sees a sunny day, maybe it should be overexposed.

No Light Meter?
-Your director tells you he needs to pick up a shot line from earlier in the day and it needs to match other takes of that shot.
-What were your key, fill and backlight reading at? Difficult with just a waveform monitor

No Monitor on set?
-You're working with Eddie Murphy and Nicole Kidman. You spot Nicole Kidmann and set your stop. Whooops! Eddie Murphy is a walking shadow with eyes. (Not quite, but you get the point and something you could've avoided with a monitor on set).

This is why I think to be really accurate in your exposure, you need a waveform monitor, a properly calibrated monitor, and a light meter. (Never base your exposure off of just your LCD, it might seem to work, but if it comes out accurately, it was pure luck).

Don't have a waveform monitor? Use your laptop. (If you've got a MAC, probably get a firewire, PC, get a USB 2.0)
-Avid has a waveform application
-FCP has a waveform application
-Don't want an entire editing system just for the waveform? Adobe has an amazing program called OnLocation that will give a really accurate waveform. It's pretty well priced for turning your laptop into a portable waveform monitor, and if you absolutely cannot afford the program, :( I don't like promoting it, but torrent it and pay Adobe back when you make money being a DP.

Don't have a professional monitor? Use a TV
-You might not have as much control over it, but you can get a pretty good 720p tv (which is probably the best setting for the camera you're using) for reasonably cheap (especially with LED TV's coming out)

Don't have a light meter? Get one
-If you're serious about being a DP, I really recommend using a light meter. Just using it really helps you understand and get used to how light works.
-If you're making movies with your friend to put on YouTube and that's it, probably don't worry about it.
-It doesn't matter if it's old or doesn't have all the features of the top of the line, but you can get a great meter for cheap.
-I've got a Sekonic L-750Cine and I love it. It's expensive, but it's got some great features. (If you're a student, Sammy's Camera will give you a discount that basically makes it half price, and I'll take a free $500 any day).

In summary
Do you need everything that I just wrote a novel about? No. But if you are serious about making an image that you can stand by, you really should have and know how to use tools to give you a quantitative and qualitative reading of what you are shooting.
 
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