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# What is Contrast Ratio, High Key and Low Key Lighting

The simplest explanation of Contrast Ratio, High Key and Low Key Lighting.

In this video and article, I’ll explain, in simple English, what Contrast Ratio means, and how it affects high and low key lighting styles.

First, watch the video:

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## Contrast Ratio

Contrast ratio as I talk about it always refers to a face.

Contrast ratio is the difference (in stops) between the brightest (key side) and darkest (shadow side) portions of a face.

Note: Many photographers use contrast ratio with different math but for cinematographers that’s useless. I always measure and talk about contrast ratio in stops. E.g., when I say 2:1, I mean the contrast ratio is two stops to one.

## High Key and Low Key Lighting

High key and low key lighting refers to the contrast of an entire scene, not just the face.

When a scene has a high contrast (great difference between the brightest and darkest portions of the face), we say the scene is low key. Lighting used to get this look is called low key lighting. Here’s an example:

On the other hand, when a scene has a low contrast (small difference between the brightest and darkest portions of the face), we say the scene is high key. Lighting used to get this look is called high key lighting. Here’s an example:

Exception: A moody scene with low contrast is not usually called a high key scene in cinematography:

Not all terminology has a logical basis. Some have just evolved over the years. The same terms in photography mean a different thing, but in cinematography, you typically find these terms used in the following way:

 Term Refers to Meaning Contrast Ratio Face Difference between brightest and darkest portions of the face. High Key Lighting Scene Difference between brightest and darkest portions of an entire scene is low, but the scene itself is bright and cheerful. Moody scenes aren’t counted. Low Key Lighting Scene Difference between brightest and darkest portions of an entire scene is high

I hope this has helped you understand contrast ratio, high key and low key lighting. Please let me know what you think in the comments below.

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## 3 replies on “What is Contrast Ratio, High Key and Low Key Lighting”

Rion Gonzalessays:

Just looking at my comments I ment to write your best. I hope you were not offended by my haste in writing. I’m very sorry if my comment was taken the wrong way.

RG

Rion Gonzalessays:

Hello there, I watched your video and for the most part it is fine. The explanation of contrast is very good. I do believe you are mistaken on the calculation of contrast ratio.

Contrast ratio is calculated at 2^ of the stop difference between the key side and the fill side. For instance, if your key is at 5.6 and your fill is at 2.8. Then you have a difference of 2 stops.

Using the above formula your calculation should look like this: 2^2 = 2×2 =4 which means the contrast ratio is 4:1.