EI Decoration vs Architecture

Under a train, a brand doc shoot with Coolbox for Northern

A few thoughts on exposure, texture, and knowing what you're giving up to get what you want.

After posting our FX3/Venice exposure test, a few people got in touch with questions. Important ones, especially to younger cinematographers. This is the follow-up—because EI and ISO aren’t just about making your image brighter or darker. They’re about shaping what lives at the extremes of your image: the texture in the shadows, the roll-off in the highlights, the mood that creeps in at the margins.

Zodiak, shot on Viper, 9-10 stops of dynamic range

Let’s get this out of the way—modern cameras are amazing. They’ve got wide dynamic range, insane low-light capabilities and forgiving sensors that would’ve been science fiction not long ago. But that doesn’t mean we get to stop thinking. When you're in control of lighting, giving up a stop or two of dynamic range won’t ruin your image—but it does change the feel of it. Just look at Zodiac (2007), shot by Harris Savides, ASC on the Grass Valley Viper. Digital was still in its awkward teenage years, but Savides leaned into its quirks, using soft light, sculpted contrast, and delicate shadow detail that worked with the sensor, not against it. The result? A film that feels haunted, analogue and intentional.

Sony Venice, Dynamic range distribution at both base ISOs

Now, let’s talk ISO and EI. Technically, ISO is a standardised rating of a camera’s light sensitivity—how much light it takes to hit “proper exposure.” Every sensor has a native ISO where it performs best. EI, or Exposure Index, is how you choose to treat that ISO in practice. It’s your working ISO—a metering decision, not a physical change to the sensor. Some cameras bake this in; others just record metadata, some can do both. Either way, EI is the lever we pull to tell the camera (and ourselves) what we care about in the image: highlights, shadows, or somewhere in between.

Rate a native 800 camera at EI 400, and you’re telling your system to expect more light because cutting from 800 to 400 halves the light. You’ll compensate by opening up a stop, lighting more or removing an ND. What you’re really doing is overexposing the sensor—pushing more signal in, getting cleaner shadows, less noise and over exposing by a stop. But you’re shaving highlight headroom. As show in the Venice dynamic range distribution chart (sexy name), we have moved middle grey down the row. That stop of cleaner shadow costs you a stop of highlight detail.

Go the other way—rate it at EI 1600—and your monitor image initially gets brighter. You might add a 0.3 ND or stop down to balance your image - if you can. But by balancing the image on the monitor you’re underexposing the sensor, protecting highlights in skies or windows or bulbs, while the shadows take a hit. Maybe they’re fine. Maybe they fall apart. Depends on the sensor and how much control of the light we have.

Hopefully that makes sense. I know it’s counter-intuitive—especially when you’re in a situation where you need more light. If you're wide open on the lens, the lights are already at 100%, your NDs are out of the matte box, and you're still short on exposure, then yes—you’ll reach for the ISO dial. And we all know what that means: more noise. But flip it. If you’ve got too much light to work with, it can be tempting to drop the EI to 400, thinking it’ll clean things up. But in that scenario, you might actually do more harm than good. Shooting at native or a stop or two over could serve the image better, depending on your highlights. It’s not always about "less noise"—sometimes it’s about protecting what matters most in the frame. The inverse, of course, is having too much light. And while it’s tempting to use EI to bring the exposure down, that only works up to a point. Every time you halve the EI—say, going from 800 to 400—you’re effectively throwing away a stop of highlight dynamic range. That could be a high price to pay just to tame a bright image and is exactly why ND filters—whether internal or in a matte box—are essential. Especially when you can’t, or don’t want to, close down the iris or dim your lighting/practicals.

Exposure control isn’t just about hitting a number—it’s about protecting the tones of the image that matter.

And that’s the thing—it’s all about intent. EI isn’t just a setting. It’s a question: What part of this frame do you care most about? What are you willing to sacrifice to protect it? Lower EI = clean shadows, riskier highlights. Higher EI = safer highlights, noisier shadows. Every choice is a trade.

Modern cinema cameras are built to be pushed. They expect us to make decisions. But once you’ve made them—once the light hits the sensor—that’s it. You can lift or crush the image in post, but if your skin tones are buried in shadow noise, or your highlights are clipped into oblivion, you’re not grading anymore—you’re doing damage control.

Only Murders in the Building, Shot on Venice

This all really matters when you want to bake in texture. Think of Only Murders in the Building—a clean-but-textured in camera look that leans on higher EI to introduce a fine layer of grain. Or flip it—when I’m lighting a space fully, I might favour a lower EI to protect the shadows, knowing I can add grain in post. Then again, sometimes I’ll say to hell with it, rate it at 5000, ND the image, and let that baked-in texture play, knowing at high base of 2500 that I’m underexposing by a stop for the texture, and I need to keep an eye on my lower end as I have less data to play with. Harsh daylight? I’ll potentially overexpose by a stop to hang onto those brutal highlights. Most of the time? I split the difference and shoot at native ISO.

From my tests with Leo Green a few months ago, overexposing by a stop makes a difference to the noise and shadow detail. Underexposing by one stop? Less dramatic with the highlights in a typical scene, but still worth noting—especially if you’re grading aggressively or dealing with a high-contrast or very bright scene. Every stop is leverage so why not use it.

Personally, I like images that feel lived-in. Maybe you do too. That’s why EI matters. You we need to know how it behaves on our camera. what it gives and what it takes. What we are surrendering, and what we are getting in return. Because at the end of the day, EI isn’t decoration. It’s architecture. And if you're serious about shaping your images with intention, it’s worth understanding every nail in the frame.