The Five Pillars of Cinematic Exposure

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There are five major ways to change exposure in cinematography:

1. The Aperture
2. The Shutter Speed
3. The ISO
4. The ND Filter
5. Lights with Dimmers

Every cinematographer manipulates one or more of these five tools to create an infinite amount of looks. Knowing how and when to use which is the first step to great cinematography.

1 The Aperture

The aperture controls the amount of light hitting the sensor. But it really exists to control the depth of field and the way it renders an image.

In cinematography, continuity plays a huge role. In a scene, from one shot to the next, there must be a continuity in the depth of field. If you like shallow depth of field, then stick to that throughout. If you like deep focus, then stick to that. Or, if you like something in between, which is what most people shoot with, you still need to maintain a similar depth of field throughout the scene. Otherwise the shots look disjointed and off.

In cinematography, the aperture typically must remain constant in every scene, or at least close enough. You can check out this video on what the best aperture is:

The bottom line is, most cinematographers look at a scene and decide an ideal aperture. Then, every shot from every angle is either at that aperture, or very close to it so the physical rendering of the shots and the depth of field match.

Different lenses behave differently at different apertures. Some are sharper at one aperture and softer at another aperture. Some flare differently. Some even show a color shift or different aberration. Knowing the right aperture to use for a scene is important, and sticking to it is even more important.

2 The Shutter Speed

To a photographer the aperture and shutter speed can change constantly, and there’s a lot of freedom.

To a cinematographer things are different. The shutter speed is typically set to emulate filmic motion blur. To get that the rule of thumb is, the shutter is set to 1 by double the frame rate. If you’re shooting at 24 fps, the shutter is at 1/48s. If the camera only allows 1/50s, then that’s fine. In shutter angle terms, you’re either at 172.8 degrees or 180 degrees. If you’re shooting 60p, the shutter is either at 1/60s or 1/125s. It depends on what look you’re after.

The reality is, most cinematographers are bound to this shutter speed and only change it if they are after some unique motion characteristic. That’s rare. The majority of the time, people shoot in 24p or 25p, and the shutter stays at 1/48s or 1/50s. Here’s more information on shutters speeds:

So there goes the second pillar of cinematic exposure. You don’t change the aperture, and you don’t change the shutter.

This is one major area how cinematography is different from photography, and the approach to exposure is different.

3 The ISO

ISO changes the sensitivity. Sometimes it’s done in hardware, and sometimes it is purely software based. What cinematographers care about is the effect.

When you raise the ISO you get more noise. Cameras also have what is called a native or base ISO, which is the ISO at which you get the maximum dynamic range and best color fidelity:

E.g., the Arri Alexa has a native ISO of 800, and the Canon EOS R5 has a native ISO of 400. If you deviate from this, you get a slightly worse image. The cheaper the camera, the worse it gets. An Alexa holds its colors quite well over a limited range. The EOS R5 or Sony a7S III does not. There’s a reason they’re cheap.

Let’s say we shoot a wide shot at a higher ISO, and the close up at another ISO, you’re going to have problems because the noise isn’t going to match.  With cheaper cameras the color or skin tone will not match either. To solve one problem you create another.

In the exposure triangle, the ISO is the third cog. I have a whole video on the exposure triangle I’m sure you’d love:

A lot of people love to correct me on ISO being pronounced “iso”. If you want to  know why I say I-S-O, then check this out:

You really want to stick to the native ISO for best image quality. That’s why most Hollywood DPs stick to ISO 800 with the Alexa, or at least 400 or 1600, which is just one stop away.  They don’t go much beyond that unless they are forced to.

So here’s a funny situation. The exposure triangle has three parts – the aperture, shutter and ISO – none of which can be changed for a scene once set!

For cinematic exposure you need the other two pillars.

4 The ND Filter

The ND filter is a piece of glass you insert at the front or back of the lens to cut down light. It comes in different powers, each reducing more light than the last.

The numbering system of ND filters is slightly complicated, similar to the aperture, and I have a cool article that will simplify it for you if you want to get into the details. The sad reality is most people will simply go back to this, the path of least resistance.

The ND filter is important because sometimes you need to cut down light but you don’t want to touch the aperture, shutter or ISO.

Let’s say you are outside shooting on a sunny day, and you want a shallow depth of field look. You crank open the aperture to f/1.4. The shutter stays at 1/50s and the ISO is at a native 400 for the best image quality.

You look at the monitor, and it’s all white. The shot is overexposed because you’re letting in too much light. You use an ND filter to cut down the extra light for better exposure.

In the long run, ND filters are a cheap way to keep using the aperture and ISO you want and  still get great exposure. If money is an issue you can buy a variable ND filter that does many ND strengths in one filter, It’s a compromise, and you’ll rarely see it on film sets, but it’s a good start to understanding how ND works.

For more information on lens filters, check this out:

The ND filter will cut light when you overexpose, but it won’t make an underexposed scene brighter. Which is why you need –

5 Lights with Dimmers

Light is what separates a cinematographer from a videographer. A videographer tries to record whatever is in front of the camera. The cinematographer specializes in creating an image to fulfill a story.

Even for documentaries or cinema vérité shooting, light can be a game changer. I have a whole guide on lighting so there’s no point in going over the details.

The bottom line is, you can  paint a scene with light, make whatever you want dark or bright, and lights that dim allow you all the freedom you need to create the image you see in your mind.

Lighting is the hardest to do. Even if you’re on a low budget, stop being lazy and carry a few lights. Make it harder for yourself, and your images will become a lot better. It will separate you from the rest of the lazy videographers who think the camera will do all the work. Tons of bloggers and YouTubers keep selling you the camera dream, but lighting is what separates the professionals from the talkers.

I hope you found this useful. Let me know in the comments below.