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Exposure without relying on a monitor (Light meter)

Exposure Light meter

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#1 Zachary Hunter

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Posted 26 March 2014 - 01:23 AM

 Hey guys, Thank you in advance for any advice I may get. I have been striving to develop my skills as a cinematographer and recently purchased a light meter to aid in achieving consistent lighting/ lighting ratios. I have yet to get the hang of using my meter or interpreting the information. I don’t want to rely on the often inaccurate monitor for judging exposure.

 

I was wondering if anybody had ideas on what would be some good exercises that would help me better understand my light meter and it’s readings because I feel some sort of disconnect between my readings and what my cameras set exposure.

Thanks.


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#2 Adrian Sierkowski

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Posted 26 March 2014 - 10:25 AM

What light meter are you using?

It's not really rocket science, for me at least. I'll often use a incident meter, and I'll stand on the talent's mark, and I'll point the lumisphere at the camera and get a reading. I know then with that reading, in that position, i'll get a "properly exposed" talent, which is nice, but doesn't help too much. From there, I'll go over to say a shaft of light and meter that, and see how many stops over or under it is, same with the dark shadows (note, sometimes you'll want to spot meter some things, but i'm keeping this pretty simple). Then one takes into account the latitude (not dynamic range) of the medium-- by latitude here we mean, how much over and under you can have something in a frame and still have it retain the important information you need without getting too grainy/noisy for your tastes. So, if we're talking film, just roughtly, you'll have more latitude in your highlights than in your shadows-- so depending on the stock you're on you may not want to let things go more than 2 stops maybe 2 and 1/2 stops under, if you still want it to be important in you scene.

From there you evaluate where to park your exposure based on how you want the scene to look.

Understanding how it will look without, well looking at it, will come with experience and is a great reason to do a camera test whenever you're starting a project, and especially if you're using a new camera!


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#3 Zachary Hunter

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Posted 26 March 2014 - 02:21 PM

Thank you for the response, Adrian!

 

 

I have the Sekonic L-758cine.

 

It's not really rocket science, for me at least. I'll often use a incident meter, and I'll stand on the talent's mark, and I'll point the lumisphere at the camera and get a reading.

That was my assumption but when out on my first test run I took some incident readings in talents location. the exposure reading seemed to blow out the talent.    I typically like to stay at specific stop and light accordingly but when I lit to that stop It seemed... wrong? 

 

 

EDIT: Using a 7D

Talent was reading at  roughly a f.2  (off the key) and I had my Iris set to 4/5./6 and it seemed to expose properly at that point. But my logic was that If they read at a f2 and I am at a 4/5.6  shouldnt the key be super dark?


Edited by Zachary Hunter, 26 March 2014 - 02:26 PM.

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#4 Adrian Sierkowski

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Posted 26 March 2014 - 02:27 PM

They should, are you sure you matched ASAs and Shutter Speeds between the 7D and the Meter? You gotta keep them the same, so on the 7D you want to use 1/50th a sec (and on the Sekonic set for 24 or 25fps, whatever you're shooting) and then match the ASA on the meter to the setting you have on the camera.

Also, and I have been guilty of this a few times, make sure you're not blocking the light yourself.


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#5 Zachary Hunter

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Posted 26 March 2014 - 03:06 PM

I have my camera at 1/40th  but i guess 1/50th would be closer to 180- what my meter is set to- now that I think about it.


Edited by Zachary Hunter, 26 March 2014 - 03:07 PM.

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#6 Guy Holt

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Posted 26 March 2014 - 05:31 PM

I was wondering if anybody had ideas on what would be some good exercises that would help me better understand my light meter and it’s readings because I feel some sort of disconnect between my readings and what my cameras set exposure.

Thanks.

 

A camera test, like the one I describe below, is good way of learning how to use a incident meter for lighting as opposed to exposure. The standard approach is to systematically test the effect of Key, Fill, Back Light, Kickers, Hair Lights, and Liners that are over and under exposure. For example, to test the effect of your key light on flesh tones, set your exposure with two doubles and a single in your key light. Then remove them a half stop at a time (without changing your camera exposure setting or exposure of the chip chart), and systematically note on a slate in the frame what you are doing. Once you have removed all the scrims, your flesh tone will be two and a half stops over exposed (since you have not changed the camera setting.)
 


camtestsubjecthor.jpg

 

Put all the scrims back in and now, using single and double nets, systematically under expose the flesh tone in half stop increments (remember rotating a net relative to the light source will make it "fatter" or "thinner", which will enable you to "dial in"with your meter the exact level you want from the light.) If you want to play on the lower register, use the meter to continue to under expose the flesh tone  in half stop increments until it becomes a pure silhouette. Do the same for Fill, Back Light, Kickers, Hair Lights, and Liners in isolation using your meter pointed directly at the light to set the level in half stop increments.

 

camtestsetuphor.jpg

 

Repeat the process for  specific combinations  of lights that you plan to use.  Having systematically tested each light, you can now see the effect that different levels of each has on the scene and have the information to use your meter to create the effect any time you like.


camtestprojectorvert.jpg

 

So that your eye does not compensate for the low light levels, you should put a fully exposed white reference in the frame (the white foam-core in the background of the pictures.) If you use a chip chart with variable gray steps form white to black, you will actually be able to see how tonal values are compressed and (block up or burn out) as you push them onto the “knee” or “toe” of your camera’s “characteristic curve.”
 

Guy Holt, Gaffer, New England Studios, Lighting and Grip Equipment Sales and Rentals in Boston.


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#7 Zachary Hunter

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Posted 26 March 2014 - 06:13 PM

Thank you Guy! This sounds like a great lighting exercise. Thank you for the time you took to post this.


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#8 Kyran Ford

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Posted 27 March 2014 - 11:57 AM

Guy always kills it with his posts -- loads of invaluable info!

 

Adrian hit the nail on the head in his first post. I assisted before electric work, and a camera assistant once told me a way to improve my distance judgement would simply be to guess the distances between objects and then measure to see how right or wrong I was. I ended up starting to use this trick (and I still do) for light. I simply eyeball the exposures, and I've developed a pretty good eye for it. Of course you can rely on the meter for accuracy with half stop or third stop increments. 


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#9 Nicholas Bedford

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Posted 28 March 2014 - 07:27 PM

One of the ways I first meter a shot is to use my incident meter and aim it perpendicular to the main light source if there is a clearly defined source such as a window or the sun. So, for example, if the sun is up early and pointing west, I meter either south or north, at 90º.

 

I do this because the most common dramatic lighting style is to light someone not silhouetted or flat on, but some off angle perpendicular to the key light. If you don't have a clearly defined light source then you want to aim the light meter at the camera itself. This will give you middle grey according to where the camera is pointing.

 

For example, in this frame I shot as a test, my meter is facing 90º from the light source but also conveniently toward the camera.

 

This means that I am getting an average exposure for my subject no matter the direction. Then, depending on the angle I am actually shooting toward the light, I can add or subtract fill or adjust my exposure for off angle shots.

 

This is just the way I do it so take it with a grain of salt. The best thing you can do, however, is to match your findings with the resulting image, as well as using a monitor with false colour or some other exposure aid.

 

light-meter.jpg


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#10 Phil Rhodes

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Posted 28 March 2014 - 07:40 PM

I quite like waveform monitors.


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#11 Adrian Sierkowski

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Posted 29 March 2014 - 12:24 AM

False color can be nice on occasion-- though personally I'll just take some zebras.


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#12 Nicholas Bedford

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Posted 29 March 2014 - 12:49 AM

False color can be nice on occasion-- though personally I'll just take some zebras.

 

I mainly use false colour to tell me where 50-59 IRE is sitting in my frame. The BMD Pocket camera I have outputs the zebra overlays through HDMI which is handy.


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#13 Adrian Sierkowski

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Posted 29 March 2014 - 12:54 AM

I recall a few times setting zebras waaayy down low to use for skin-tones, before switching them out to check for exposure on highlights. Though on the pocket I just meter it for 800 as I would film.


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#14 Brian Drysdale

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Posted 29 March 2014 - 03:23 AM

The Arri Alexa has a rather neat zone system.

 

Yes Guy does great posts, he should put them as a blog on his web site.


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#15 Jon Whitford

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Posted 29 March 2014 - 07:26 PM

Experience will help.  The biggest thing I wish I'd been doing is making a note or checking of footcandles or lumens each time I took a reading.


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#16 Igor Trajkovski

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Posted 29 March 2014 - 08:30 PM

Check these 2 articles by Art Adams:

Trusting My Meter: The Perception of Brightness

 

and the new one:

The Art Adams Zone System for HD

 

 

Regards

 

Igor


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#17 timHealy

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Posted 31 March 2014 - 08:05 AM

Experience will help.  The biggest thing I wish I'd been doing is making a note or checking of footcandles or lumens each time I took a reading.

 

 Ahhhh  foot candles… An old spectra and reading foot-candles is a classy and elegant way to work.


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#18 Stephen Murphy

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Posted 31 March 2014 - 09:20 AM

Take a look at this video from Mark Vargo ASC - it might help you a little bit
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#19 Michael LaVoie

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Posted 31 March 2014 - 12:39 PM

Even if you want to learn this without a monitor on set, you still will have to look at the footage to know what you got.  So if you take notes with your meter during some test shots, you can use the waveform in post and cross check where skin tones fall on your waveform.  Since that's the definitive signal after the fact.  

 

You may like skin tones to key in the 50's, possibly the 40's depending on the look, time of day, etc.  A night scene and you may want them in the 30's.  It all depends on the style.

 

A Matrox I/O box can turn a crap computer monitor into a decent representation of what you have and that will further help you understand the waveform and what those IRE values mean to you visually.  Then, at least you'll have a way to check the results of what you're doing with the meter.

 

As you get better with your meter, you'll find that when you do the post work later, you're manipulating that waveform signal less and less because you're more accurate with your readings on the day.


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#20 David Auner aac

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Posted 04 April 2014 - 03:49 AM

Quoting Adrian above:

It's not really rocket science, for me at least. I'll often use a incident meter, and I'll stand on the talent's mark, and I'll point the lumisphere at the camera and get a reading. I know then with that reading, in that position, I'll get a "properly exposed" talent, which is nice, but doesn't help too much.

 
Well, actually no. that's not quite true mate. Your meter is calibrated to about 12%-15% reflectance (depending on make and model and not 18% as everybody assumes and almost every books says!). And "average Caucasian" skin reflects about 35% of the light. So to get "proper" exposure you'd have stop down about one to 1,5 stops. Put in Zone System terms this means your meter assumes a Zone V but a face actually should fall into Zone VI so you close down one stop to put it one Zone higher "up"!
 
Best, Dave

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