Standardizing Exposure with the El Zone System
You often hear “take it three stops down” or “four stops over,” but what does that actually mean?
Throughout this interview, the two ASC cinematographers discuss the lack of specificity in IRE values, waveform monitors, and false colors. In fact, they’re not consistent from one monitor manufacturer to the next. Lachman explains how the El Zone System changes all that and brings the cinematography world into perfect harmony.
CINEMATOGRAPHER ED LACHMAN, ASC
If you don’t know legendary cinematographer, Ed Lachman, ASC, you certainly know his work. The acclaimed director of photography has lensed iconic films like I’m Not There, Carol, The Virgin Suicides, and Erin Brockovich.
WHAT IS THE EL ZONE SYSTEM?
The El Zone System is an intuitive, innovative, and essential exposure tool that helps cinematographers accurately gauge exposure by systematizing its values. It’s based on 18% gray, the universal standard for photography. Similar to a spot meter in your viewfinder or monitor, you can toggle it on and off as you please.
|PRO TIP: Print out the ROY G BIV rainbow and tape it to your monitor or EVF.
- White — Over-exposed by 6 stops or more
- 18% Gray — Normal-Neutral
- Black — Under-exposed by 6 stops or more
LACHMAN’S APPROACH TO EXPOSURE
Around 50 years ago when Lachman was in art school, he wanted to figure out how to create a style and look with latitude and exposure. When he observed his environment or looked at paintings, photographs, and other films, it felt like a mystery. He wondered how did they create that exposure range and latitude?
At the time, he referenced Ansel Adams’ Zone System. He was able to place the negative where he wanted the exposure to read the shadow and highlight details and not lose one for the other.
So, Lachman created his own system. Back then he would shoot 3000 ASA Polaroids and his gaffer John de Blau (who he still works with to this day) worked out on the back of the Polaroid camera what ASA he worked with to what stop. There was a scale that would equate the exposure.
When Lachman thought about it, he realized the Polaroids were almost like Rec.709 because they didn’t have the range that a negative would. But they would put him in the area where he had exposure. The Polaroid essentially places a “LUT” on the image.
Lachman would write the ASA of the film stock and read it with his spot meter. Then, he would write the actual stop on the Polaroid. So, he had a visual reference which now you can do through your camera since today the camera itself functions like a spot meter.
EXPOSURE IN THE DIGITAL AGE
In the past, cinematographers kept a detailed light book to record where the lights were, the ASA, exposure, etc. for when they would return to a location. So, when the digital revolution struck, Lachman wondered how he would understand exposure in this new age of digital capture. He didn’t want to only rely on a DIT and camera manufacturer. He wanted to have control of the range and exposure. When he shot on film, he had the ability to adjust the look.
For over 10 years, Lachman conveyed his concerns to different camera manufacturers. Barry Russo at Panasonic (who started out as a DIT) loved the idea. That’s because every manufacturer has their own interpretation of color and false color. When Lachman researched IRE, he discovered it stood for International Radio Engineers and used it to track lightning!
So, basically, cinematographers are judging their exposure based on radio signals. While we often use Waveform monitors, they show the curvature of the exposure but they fail to map the exposure exactly to what your frame is.
“When SmallHD came on board with this, it was a godsend, because now I could map the exact exposure of the frame in stops. Because everything that we work with, we still [do so] in stops.”
Now that it’s in monitors and cameras, Lachman is pleased to see how the El Zone System is taking off.
THE ADVANTAGE OF THE EL ZONE SYSTEM
According to fellow ASC cinematographer, Shane Hurlbut, “This is a no-brainer for cinematographers. That immediately we’re going to know, ‘Oh, that’s six over? Okay, gotcha.’” —Ed Lachman, ASC
Hurlbut also notes how Lachman’s El Zone System makes pickups easier as well as additional photography because now you will know exactly what your contrast ratio is.
Lachman pulls out his spot meter in the studio at 800 ISO and reads between 4.2 and 4.3 stops. The most important part of the El Zone System is the 18% Gray because it sits at the center of the exposure range.
Lachman fashioned the scale to include half a stop between the 18% Gray, because for him the most important part is the flesh tone.
There are other systems that try to do what Lachman has created with the El Zone System, but they’re based on IRE.
The problem with IRE versus logarithmic stops is that IRE is linear — i.e. 0-1 or 0-10. So, 2 to 2.8 is 0 – 1, and 2.8 to 4 is 0-1. That’s why there’s always a discrepancy when you use your meter on set, it never matches. But Logarithmic means you double the amount of light. When you go 2 to 2.8, you double the amount of light. When you go 2.8 to 4, you’ve doubled the amount of light.
“From a light standpoint,” explains Hurlbut, “if I want another stop, say I have a 5k that’s keying us. If I want another stop, I need to add another 5k. I can’t add a 2k. I have to add another 5k to actually add one stop. A lot of people don’t really understand that.”
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