Waveforms over Histograms, any day of the week.

When it comes to exposure, there are two mainstream approaches. One can expose to the right, while the other approach allows one to expose for middle grey. Exposing to the right, also known as ETTR, is typically achieved by using a histogram, while exposing for middle grey is better achieved by using a waveform monitor.

Histograms

A histogram shows information horizontally, the blackest black on the left, and the brightest white on the right. Using a histogram is a common, and valid, approach for lots of circumstances. My issue with histograms is that they don’t show us WHICH parts of the image are dark or bright, just how much of the whole image is exposed at each value. While the exposure for a certain scene might be correct, the overall exposure most likely would be inconsistent from shot to shot. This might not be an issue while shooting stills, but it can be when shooting video.

Waveforms

Unlike histograms, waveforms do represent an abstract version of the image. The waveform’s data on the left mirrors exactly what’s on the left of the frame, what’s at the bottom of the waveform mirrors what’s at the bottom of the frame, etc. You can use the tiny monitor on your camera, or you could use a properly calibrated, large and bright external monitor/recorder. Totally up to you. =) Regardless the viewing device, let’s compare a standard “tonal range ramp” on a Histogram and on a Waveform Monitor. Even though the image goes from pure black to pure white (from left to right) the histogram is just showing us the overall exposure. On the contrary, on the waverform monitor, we clearly the tonal range going from 0 to 255.

This is why I prefer to expose for middle grey using a waveform monitor. An essential tool I always carry with me is a ColorChecker Passport Video, a scientifically designed chart that helps me quickly determine my whites, middle greys, and blacks from shot to shot.

This approach becomes even more critical if we are shooting LOG. There’s a lot of latitude when shooting LOG, but that doesn’t mean you don’t need to expose it properly! If you bury things down at the bottom of the waveform, most likely it will be gone.

We can’t simply judge exposure by looking at the image, so we MUST understand where the values for that particular camera should fall, and there’s no better way to “measure” them than the exact values provided by a ColorChecker Passport Video and measured by a waveform monitor.

Typical Exposure Recommendations for REC 709

• 100 IRE Highlights
• 70 IRE Caucasian Skin Tones
• 45-55 IRE 18% or Middle Grey
• 0 IRE Blacks

Exposure Recommendations for LOG

• 80 IRE Super White
• 61 IRE White
• 55 IRE Caucasian Skin Tones
• 42 IRE Skin Tones
• 15 IRE the lowest IRE to avoid Noise
• 7.3 Black

You have to trust your tools, and a waveform never lies. The waveform is also agnostic; it doesn’t matter which camera brand or model, frame size, or aspect ratio you use, all waveforms will look the same.