Previsualizing:
Dialogues with Light Meters
and the Zone System

by Rick Wise
See also: How to use the Zone System

While light meters are guides to correct exposure, they are also tools to previsualize the scene you are about to film. As every cinematographer soon learns, there are two basic kinds of light meters: incident (which measures light falling onto the subject), and reflected (which measures light bouncing back from the subject.) For many years I've found myself in a constant dialogue between my two main meters, a Spectra for incident readings, and a Pentax spot meter equipped with a Zone-Vl* dial to read reflected light values.  

In general, the Spectra is a wonderful instrument to judge the intensity of light falling onto a face, and gives an accurate exposure. But lighting scenes depends on truly visualizing what you want the final print or TV-image to look like. Here's where the famous Zone system, developed long ago by still photographer Ansel Adams, comes in so handy. He observed that you can make any surface appear black, or white, or any gray in-between, depending on how you expose (and process) the negative. He found that for the film he was exposing and the paper he was printing to, he could divide the range of black-to-white into 10 zones, with 0=black, lX=white. Each zone change = roughly 1 stop. 

Modern film stocks approximate this range. For examples, 5245 is a marvelously fine grain stock, but it is very "contrasty," and a change of 1 stop will change more than 1 zone, especially toward the black (Zone 0) or white (zone lX) end. The new 5277 curves slowly toward the blacks, and whites, and so it takes more than 1 stop change to reach a new Zone.  

By and large, depending on the film stock, when exposing for transfer to tape through a Rank, Zone V = middle gray; in-between Zone V and Zone Vl = many Caucasian skins; Zone lV to Zone V = many black skins; Zone Vll = textured white, high Zone Vlll to lX = pure white or "clip";  Zone ll or lll = textured black; blue/green screen = Zone lV for most post houses. 

The challenge for us all is to pre-visualize. When you look at the scene you're about to film, ask yourself: where do you want this part of the face to expose? Where the brown column? Where the bouquet of white tulips? Where the silver ladle? Where the ochre wall? We learn to turn multiple color fragments into multiple black-and-white fragments, each falling where we pre-visualize on the gray scale. 

In practical terms, how do we shape that scene? We start by deciding on the dominant light, the dominant value - usually set by a "key" light. Once we establish that key, then all that's left to do is control the light falling on everything else in the scene. We might want the face to be "normal", and so we set our exposure accordingly -- so that a Caucasian face will photograph somewhere between Zone V-Vl (depending on how ruddy, or how pale) and an African-American somewhere around Zone lV  or V (again depending on how dark or light.)

Now we look at all the other elements in the scene. With practice, without using a meter we can see that the vase of tulips is too bright, and ask to have it scrimmed down 1-2-3-4 stops, as our practiced eye sees it. Then we can check it with our spot meter - perhaps now it reads Zone ll, just perfect for this moody scene. Or perhaps we want this vase of tulips to bloom brightly, aided by a fog filter, and instead of scrimming it down, we want to bring it right up into Zone Vlll. In that case, we may need to add a "special," a small light just for the vase to bring it up to Zone Vlll. And so on, through every visual element in this scene that we have time to control.

Every DP faces the decision on every scene: can I take more time to finesse the details of this scene, or do we have to shoot now, the way it is? In time we learn to quickly set the broad strokes right, learn where to set the key, scrim or flag-off large areas we want to darken, add a "special" here or there, and we also learn to evaluate whether or not we can take some more time to adjust the particular details. It's up to us to tell the director or assistant director or producer, "OK." And stand by that decision.

At the start of this short discussion, I observed that I hold a conversation between my Spectra and my spot meter. It's actually a 3-way conversation: the eye, and the two meters. It never ends.

*Zone Vl seems to have been bought out by CalumetPhoto.com.   When you reach their web page, enter "zone meter" to get a list of items on this subject, including the overlay zone dials which still costs $3.  They also make an excellent leather holster for the Pentax for around $30 (on sale 5/16/00 for $19.95 -- no idea how long this price will last.).  Go to the meter page first, then click on the holster.  The Soligar holster listed in the main section is NOT the leather one.  By the way, they charge much too much  (I think) for shipping and handling. But the item prices are more than fair, so maybe it all works out.

For a full explanation of the Zone System, see The Negative by Ansel Adams.  Zone Vl sells the book for $19.95 + postage. Amazon.com (http://www.amazon.com ) sells it for $17.56 + postage.

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