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Light Meter? But I'm Shooting Digital...

By Dan Coplan, SOC

Sekonic L-398M Studio Deluxe II
Sekonic's L-398M Studio Deluxe II is designed for still and cinematographic use.
There's a common misconception that a light meter is obsolete for today's digital video production. Video monitors provide WYSIWYG feedback of what the camera sees and what is ultimately laid to tape. Waveform monitors take the process a step further by showing the scene's luminance in a form you can use to objectively analyze the entire tonal range. A properly calibrated light meter, however, is an invaluable tool for planning a shoot and maintaining the quality of images throughout production.

The first step in setting up your meter is to determine the ASA, or light sensitivity, of your camera (see end of article how to do this). Dial this number into your light meter. You will also need to set the shutter speed. If shooting 24P, the shutter speed you choose will most likely be 1/48 of a second. This represents the common 180 degree shutter of a film camera. Meters specifically designed for cinematography will allow you to dial in both the frame rate and shutter angle. With meters designed for still photography, you may have to use the closest shutter speed and take the offset into account.

With the above values set into the meter, all that's left is to measure the light intensity and determine the aperture. The reading of the meter translates to a properly exposed gray card that falls in the middle of the tonal scale from black to white. This information can then be used to make a variety of informed decisions about the amount of light necessary for your shoot. Note: Due to variations in camera setup, ASA values may differ between indoor and outdoor lighting so test both!



When scouting locations prior to production, a light meter allows you to determine the amount of light available at any given time. Assuming conditions remain the same, you can decide whether additional light is required to supplement existing illumination or if you'll need to control the light directly, with filters, or other means. As an example, a scene I was shooting involved an actor under a street light at night. To the director's and my eyes, the street lamp appeared sufficiently bright. My meter, however, indicated there was barely enough light for a faint image. Thanks to my meter we saved ourselves wasted time and I saved myself a lot of embarrassment.

Our eyes constantly adapt to various conditions and can see much further into shadows and highlights than video or film. Therefore, it's not wise to rely on eyesight alone in judging exposure. That lesson was learned from a previous project... Supplied only with the camera's onboard LCD monitor for reference, I recorded an image that looked perfectly exposed. Back in the edit suite, however, the image revealed itself as greatly underexposed. This taught me lessons both about confirming exposure with my meter and the need for properly calibrated production monitors when judging exposure on screen.

Consistency is key. As you're shooting, it's a great idea to keep notes about the light values in the scene. If you need to return to the same setup at a later time, your notes will allow you to recreate the scene precisely. I've been caught a couple times coming back to a scene with little recollection of the original set up. Notes are also a life saver for illumination that suddenly changes. Imagine getting halfway through a scene on a sunny day; all of a sudden the clouds roll in, the background gets darker, you lose your nice backlight... With a good set of notes, you can intelligently make camera and lighting adjustments and have a better chance of maintaining the same look.

When shooting blue or green screens, the more consistent the background, the easier it will be for post production to pull a clean matte. Additionally, some post houses like the background to be a particular intensity above or below your key light. A light meter will insure you're exposing all the elements to spec.

Finally, for those interested in the craft of filmmaking, understanding light and how its various qualities affect everything we see contributes to our overall sense of accomplishment. With greater understanding comes greater satisfaction and quality of work. Not to mention, it's cool running around with your mysterious little gadget, sticking it in the face of high paid actors and CEO's.

How to Rate a Camera's ASA
Auto Iris
1. Frame up a gray card.
2. Activate the camera's auto iris. It will adjust the iris to provide an exposure that's equivalent to middle gray. Some cameras allow you to add over or under exposure compensation to this function so make sure you normalize this setting first.
3. Set the appropriate shutter speed on your light meter. Hold the meter against the gray card and face the white sphere towards the camera. Read the light level.
4. Adjust the ASA setting on the meter until the iris reading on the meter matches the iris reading on the camera. This is your ASA.

Waveform Monitor
1. Frame up a gray card.
2. Adjust the camera's iris until the waveform monitor displays a line going across 50 IRE. This is middle gray.
3. Set the appropriate shutter speed on your light meter. Hold the meter against the gray card and face the white sphere towards the camera. Read the light level.
4. Adjust the ASA setting on the meter until the iris reading on the meter matches the iris reading on the camera. This is your ASA.

Built-in Spot Meter (only available on some cameras)
1. Frame up a gray card.
2. Activate the camera's spot meter. Not all cameras have this function. The Varicam and SDX-900 have a "Y GET" function. The DVX-100 has this as the third option when you toggle the zebra button. Adjust the camera's iris until the spot meter function reads "50". This is middle gray.
3. Set the appropriate shutter speed on your light meter. Hold the meter against the gray card and face the white sphere towards the camera. Read the light level.
4. Adjust the ASA setting on the meter until the iris reading on the meter matches the iris reading on the camera. This is your ASA.

Dan Coplan, SOC is a Cinematographer /Digital Imaging Tech. Read more about him at his website, www.dancoplan.com

Copyright 2005. Dan Coplan.


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Related Keywords:light meter, 24P, digital video, film camera, cinematography, ASA, , Video monitors, Sekonic

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