How do you define "key light" on character's face?

PING-CHUAN CHOU · August 29, 2022

I have a question about the key light? Is it the brightest light on character's face? or the large coverage on character's face? or neither of them is correct?

Stewart McLain · August 30, 2022

The key light is the primary light on whatever your subject is. If you have multiple lights on a subject's face, the key will be the brightest one.

Google "three point lighting" and you will find lots of good examples of basic lighting setups that include key, fill, and backlight.

PING-CHUAN CHOU · August 30, 2022

Thanks for replying me. I understand the three point lighting. I am thinking if the light on the subject is very soft, even and you can't even tell where the light comes from. However, the character has a kicker light which is the brightest on the head. Will you call it key light? It's a shame I delete the picture reference for more discussion.

Stewart McLain · September 1, 2022

My inclination would be to refer to backlight as backlight regardless of how bright it is in comparison to the other lights. Even under "normal" lighting scenarios the backlight may be a stop or two brighter than the key. The way I think about it, the key and fill illuminate the front-facing portion of the subject and backlight is always behind it.

It's possible some people might call a subject lit only by backlight as being "keyed by backlight" or something like that. I wouldn't but I would understand what they meant if someone said that to me.

Stephen Sanchez · September 26, 2022

On 8/30/2022 at 7:46 PM, PING-CHUAN CHOU said:

Thanks for replying me. I understand the three point lighting. I am thinking if the light on the subject is very soft, even and you can't even tell where the light comes from. However, the character has a kicker light which is the brightest on the head. Will you call it key light? It's a shame I delete the picture reference for more discussion.

I know this is late, but perhaps it can help others who search it.

A key light is the principle source (or sources) used to bring the face to exposure. Its intensity and size have no rules. Its exposure level has no rules. It may be brighter or dimmer than the back light. In order to see the face, light must fall on it to reflect into camera, so a minimum angle to camera is 90 degrees.

Fill is the rest of the environment that surrounds the face. Although the opposite of key tends to be made darker for contrast. In some cases, the face can be fill only, with no key side.