Don’t ETTR, Use a 50% Grey Card

ETTR (Expose To The Right) can reduce the quality of your film and make life complicated for whoever’s colour grading the pictures. Instead I’ll be using a middle grey card (50% grey) along with the waveform scope and false colour tools you find on cameras and monitors. I’ll explain how a middle grey card helps you expose natural looking skin tones.

In this article, I’ll explain why I don’t ETTR and use a grey card instead. I’ll explain what Expose To The Right (ETTR) does to your pictures, then I’ll show you a powerful and simple alternative. Start achieving excellent and consistent cinematic exposure on your next movie project. If you’re working as a cinematographer on a fiction film, you need to be shooting great quality pictures with consistent exposure. Not only does it maximise the quality of the pictures but also makes you the colourist’s best friend.

Whether you’re working with a cinema camera, a broadcast camera or a mirrorless camera, you can shoot with a High Dynamic Range (HDR). Because more filmmakers are shooting HDR and most films are colour graded, it’s important we expose our shots correctly. But there’s conflicting advice out there about how to do that. PersonalIy I think Expose To The Right is harmful to your film and also a headache for the colourist. Unfortunately I still see it being taught and recommended to beginner filmmakers. It’s an out of date technique that can be easily replaced by something better.

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What is ETTR and Why is it Bad?

ETTR was a popular technique when shooting Standard Dynamic Range (SDR) video. The idea is you over-expose the picture as much as possible without clipping the highlights. Clipping is where you lose detail forever in the brightest areas of the image. The image below shows what ETTR looks like on a Histogram. The over-exposed trace is more over to the right, which is where the term comes from.

Histogram showing ETTR - Indigo Film School
Histogram showing ETTR

Because Standard Dynamic Range only has 6 stops, this exposure technique worked okay. It stops detail getting lost in the shadows and avoids clipping the highlights. But now we’re shooting with HDR, the typical dynamic ranges is 12 to 15 stops. When you’re working with such a big latitude, Expose To The Right can create complications for you and whoever’s grading the film.

ETTR and Inconsistent Exposure

Important details such as skin, clothes, walls, furniture are all in the mid-tones. When you Expose To The Right, you’re prioritising the brightest part of the image, which is less important. It causes inconsistent exposure of the mid-tones, which then lead to problems when grading the project.

Let’s imagine I’ve shot a few scenes in different lighting conditions using Expose To The Right; exposing to the brightest areas of the image. The maximum brightness varies between shots. In general, highlights are brighter when shooting exteriors and darker for interiors. Using ETTR on bright exterior shots can under-expose mid-tones. And using it on darker interior shots can over-exposure mid-tones. This creates a lack of consistency between shots.

ETTR and Inconsistent Picture Noise

Let’s imagine the colourist has corrected the mid-tones so they’re all pretty much in line. They’ve made some scenes brighter and some darker to match mid-tone levels between scenes. It’s made the shots more consistent. But changing exposure in colour grading software is like shooting with different ISO settings. It creates inconsistent picture noise between shots.

To learn more about ISO, watch this video: What is ISO?

Making some shots brighter in the grade has increased noise. While making other shots darker has reduced it. The differences might be obvious or they might be more subtle, but these variations will be picked up by the audience and it can make the film feel less professional.

These issues can be solved during post production. In editing or grading software, you can use a noise reduction filter, or alternatively a filter that adds noise. But these can reduce the overall quality of the film, or they can compromise the look you’re trying to achieve.

ETTR and Inconsistent Colour Saturation

Another problem created by Exposing To The Right is inconsistent colour saturation. Saturation defines the richness and purity of colour in an image. You can see what happens on this diagram. The diamond shape represents the range of colours and brightness your camera can record. The vertical axis is exposure and the horizontal axis is colour saturation.

Colour saturation affected by picture brightness diagram
Colour saturation is affected by the brightness of the image

Colours in the the mid-tones are the most saturated, shown by the widest part of the diamond. As you move up into the brighter areas of the picture, the colours narrow and become less saturated. The same thing happens when you move down into the darker areas of the image.

Because shooting with ETTR gives you inconsistent mid-tone levels, you’ll also see inconsistent colour saturation between shots. This can be adjusted in the colour grade, but it’s time spent fixing problems instead of enhancing the look of the film.

How to Shoot with Consistent Exposure

Now we’ve seen what problems ETTR can create, let’s look at how you can get consistent exposure while prioritising the mid-tones.

To get the mid-tones to line up, I use a middle grey card. Middle grey is a well defined brightness level that we can use to anchor our exposure. It’s also known as 50% grey, or an 18% card. This is because it reflects 18% of the light that falls on it. The example below, is the Ezybalance from Lastolite. You can use whatever grey card you prefer, just make sure it’s professional quality.

50% grey card, middle grey, 18% grey
Middle grey card. Also know as 50% grey and 18% grey.

Exercise: Exposing with a Middle Grey Card

This is an exercise you can try yourself. Here’s the setup and the camera settings I recommend:

  • Setup in a well lit location, either exterior or interior
  • Attach the camera to a tripod, so you don’t have to shoot handheld
  • Make sure you’re shooting in a high dynamic range, either Raw or 10-bit Log. An 8-bit format isn’t true HDR.
  • Set the camera to the recommended native ISO. This is often 800, but check the manual, because it varies from camera to camera. If your camera has dual native ISO, pick the lower value.
  • Set the frame rate to 24 frames per second, which is the standard for a movie.
  • If your camera uses shutter angle, set it to 180º. If it uses shutter speed, set it to a 48th of a second.
  • Use the aperture and if necessary ND filters to control the exposure. 

Place the grey card close to the subject’s face. That way it’s getting the same light as the subject. It needs to be face-on to the camera, not at an angle.

You can then use exposure tools on your camera display to set exposure. I’ll show you how with a waveform and false colour.

Setting Exposure with the Waveform Monitor

A waveform is a professional video scope. You can usually display this on your camera monitor, or on a professional preview monitor. It looks like this. The horizontal axis represents the picture. The traces on both sides are the blue pillars. In the centre is the character holding the Ezybalance card.

The vertical axis represents brightness levels. Highlights such as the bright edge of the Ezybalance, have a higher trace. Darker areas such as the background have a lower trace. On the waveform, the grey card appears as a straight line. It’s not always this well defined. Depending on the lighting, it might appear as a fuzzy line.

If your waveform has a percentage scale, adjust the aperture until the grey card is at 38%. If your waveform has an HDR scale, adjust the exposure until the grey card is at 26 nits.

About Brightness Values

Let’s just pause for a moment to clarify these values I’m using.

38 percent or 26 nits are general recommendations for middle grey when shooting in HDR. By using them, you will get good results. However, the middle grey value recommended for your camera might be slightly different.

Let’s imagine you’re using a Sony camera and shooting in S-Log3. You need to find out the middle grey value recommended by Sony when shooting in S-Log3 and with the camera set to its native ISO. It won’t be far off 38 percent, but it’ll be slightly different. But for now, you can stick with 38 percent or 26 nits.

Setting Exposure with False Colour

Let’s look at how you can use false colour to set exposure. This is an overlay you can activate on your camera monitor or a professional preview monitor. When you use a false colour overlay, different colours represent different exposure levels. Most cameras and monitors have adopted the Arri colour scale, but they can vary.

False colour - Arri scale
Typical false colours, based on the Arri scale

If green represents middle grey, adjust exposure on your camera until most of the middle grey card is overlaid in green.

  • The first character has fair skin, so we would expect to see pink on their face. That’s because, on average, fair skin is one stop above middle grey.
  • If the character’s skin is brown or olive, you would expect to see grey on their face, showing that the skin tone as half a stop above middle grey.
  • If the character’s skin is dark brown, we’ll see areas of green on their face, showing their skin tone is the same as middle grey.

So by using the grey card, you’ll find that different skin tones are exposed correctly.

When you expose to middle grey, it doesn’t mean you can’t over or under-expose the picture. After all, different scenes in different locations require different approaches. But I recommend that for each scene, you try to expose your shots consistently. So if you over-expose the first shot, try to over-expose all the other shots in the same scene to remain consistent.

Controlling Shadows and Highlights with Lights and Lighting Modifiers

Once you’ve set the mid-tones, you can use lighting techniques to control the shadows and highlights in the picture. You can increase brightness in the shadows with artificial lights and you can decrease highlights by using flags or nets.

Two professional lights
Two professional lights

You don’t need to spend a fortune on this type of equipment when starting out. You can find cheap video lights online and anything that blocks light can be used as a flag. Dark material with fine holes can be used as a net and white translucent material can be used as diffusion.

When you make adjustments to the light levels, always check the exposure on the camera.

Summary

So the technique I recommend for achieving consistent, cinematic exposure is shooting a grey card. Try it out for yourself. With practice, working this way will become second nature.

If you’ve got any questions or suggestions please comment.

Go Further

If you found this useful, check out the rest of my fantastic Camera Training videos:

Return to Cinematography Training page


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