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#1 Daniel Moore

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Posted 02 November 2008 - 01:09 AM

I have some basic questions. If people could give me some replies that would be great.

What's "motivated" light?

What's a "Fill" light?

What's a "Key" light?

Is a "Back" light even necessary if you don't want a silhouette?

I take it from what I have read that there are no official positions for the lights to be set up....so would the lighting names (Fill, Key, etc) not change based on their physical positioning?

I was watching The Terminal(with Tom Hanks), and there's a scene where Tom Hanks is walking with whoever plays the security guard. They are walking down a hallway in the airport and there's a ton of light pouring in from giant windows behind them as they walk towards the camera(the camera is moving backwards as they walk forward). I think the light lit up the whole hallway, but both Tom Hanks and the other guy were completely lit in the scene- so because the light was behind them(which I don't know if it was real sunlight or a really huge set light), does that make it a "Back" light, or does it make it a "Key" light because it was the main source of light in the shot? I'm guessing it was also the only light, because if the camera was moving down the hallway for the shot, other lighting set ups would probably logically been on camera haha.

If people could be elaborate that would be great. Thanks!
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#2 Daniel Sheehy

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Posted 02 November 2008 - 03:37 AM

Motivated light - light which has 'motivation' or a reason for it's placement / use. [ie. a lamp in shot, the sun, moon, car lights etc]

Key - as you've already said, the main or primary light source.

Fill - light used to lower contrast in the image by filling in some of the shadow areas left by the key light.

The use of the back light is always debated here, it boils down to taste and motivation. What does the script need?
A back light might be clearly motivated by the location or story, or it may be used without motivation to provide separation between foreground and background elements.

The lights are named according to the function they perform, not physical location. So you could key a character with a back light.. for example as in the shot you described from Terminal. This is then balanced out with fill light to enable the character's face to be seen (as per your desription).. or not, if a silhouette is desired.

Edited by Daniel Sheehy, 02 November 2008 - 03:38 AM.

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#3 Andrew Koch

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Posted 02 November 2008 - 03:54 AM

Daniel explained it great. I would just like to add something because I remember this being a confusing thing when I was in filmschool. Backlight is in reference to the camera direction. If a subject is facing the camera and the light is behind them pointed in the direction toward the camera, the subject is being backlit, but here is where it can get confusing. If the actor has his/her back to the camera and the light if shining on the actor's face in front of him/her, this is still backlight because the light is still shining toward the camera. The light is still functioning the same way. So, as Daniel said, it is the function of the light that gives it it's name.
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#4 Tim Terner

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Posted 02 November 2008 - 04:34 AM

2 very well explained definitions. Also to add that what starts off as a backlight in a shot with a moving camera can end as the keylight
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#5 Daniel Moore

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Posted 02 November 2008 - 12:40 PM

Motivated light - light which has 'motivation' or a reason for it's placement / use. [ie. a lamp in shot, the sun, moon, car lights etc]

Key - as you've already said, the main or primary light source.

Fill - light used to lower contrast in the image by filling in some of the shadow areas left by the key light.

The use of the back light is always debated here, it boils down to taste and motivation. What does the script need?
A back light might be clearly motivated by the location or story, or it may be used without motivation to provide separation between foreground and background elements.

The lights are named according to the function they perform, not physical location. So you could key a character with a back light.. for example as in the shot you described from Terminal. This is then balanced out with fill light to enable the character's face to be seen (as per your desription).. or not, if a silhouette is desired.


Thanks guys, awesome responses. I thought things like car lights, and a lamp in the shot were considered "practicals"....?

Also, now that I've read the responses and I think about that scene from The Terminal, it seems like the names of lighting functions are to an extent, semantics. Meaning, a light in the back of a scene is not necessarily a "Back" light just because it's in the back. It just turns into a debate about perception. That scene I described from the Terminal had all that light behind Tom Hanks and the other guy, but, I think to myself that maybe it was possible that although it was a light behind the actors, for all I know the DP could have intended to actually have the lighting aimed towards their faces be the key light? Unless, the strongest light in the shot(light from behind them) automatically becomes the key light because it's the strongest source....

Edited by Daniel Moore, 02 November 2008 - 12:41 PM.

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#6 David Mullen ASC

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Posted 02 November 2008 - 01:19 PM

A "backlight" is a simple concept, a light that comes from the background or behind the subject, aiming towards the camera.

"Key" is more confusing or vague since it means the "primary" light on the subject - there are cases where the "key" is a backlight, or you could say that there is no "key" I guess. Or the strong backlight bounces back up into the subject's face -- now is that bouncelight into the shadows the "fill" or is it the "key" since it the the main light on the subject's face? Or is the key the backlight since it is the dominant light in the scene?

"Silhouette" is different than backlight -- in fact, technically a silhouetted subject would not be backlit, they would not be lit at all -- a silhouette is a solid black shape against a lighter background. So if you lit the background and let the subject be a black cut-out shape in front of that, they would be a silhouette. Though some people are more vague in the use of the term to describe anytime the subject is fairly dark against a lit background, though not necessarily black and sometimes backlit.
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#7 David Rakoczy

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Posted 02 November 2008 - 01:22 PM

Order the book FILM LIGHTING by Malkiewicz
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#8 Daniel Moore

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Posted 02 November 2008 - 02:48 PM

A "backlight" is a simple concept, a light that comes from the background or behind the subject, aiming towards the camera.

"Key" is more confusing or vague since it means the "primary" light on the subject - there are cases where the "key" is a backlight, or you could say that there is no "key" I guess. Or the strong backlight bounces back up into the subject's face -- now is that bouncelight into the shadows the "fill" or is it the "key" since it the the main light on the subject's face? Or is the key the backlight since it is the dominant light in the scene?

"Silhouette" is different than backlight -- in fact, technically a silhouetted subject would not be backlit, they would not be lit at all -- a silhouette is a solid black shape against a lighter background. So if you lit the background and let the subject be a black cut-out shape in front of that, they would be a silhouette. Though some people are more vague in the use of the term to describe anytime the subject is fairly dark against a lit background, though not necessarily black and sometimes backlit.


Hmmm, well in that case, it seems like there could in some cases be no lighting function names at all. If I light a scene with all candles as practicals, there would be no back light, no fill light, but maybe you could consider the practicals to be the key lights because they are not only the primary source but the only source. It seems like all those function names are for when and/or if someone might use them to make describing a very average/basic lighting set up...like for an interview, but it seems to become more vague when I think of these functions being translated into movies....

Also, thank you Mr. Rakoczy for that book recommendation, I will check that out

Edited by Daniel Moore, 02 November 2008 - 02:51 PM.

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#9 David Rakoczy

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Posted 02 November 2008 - 03:00 PM

You will find it most en-Lightening... the latest version has been updated by Mr. Mullin.

Enjoy...
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#10 David Mullen ASC

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Posted 02 November 2008 - 04:38 PM

I helped Kris Malkiewicz update his book "Cinematography" (which has an updated chapter on lighting) -- but he's currently working on a revision to "Film Lighting."

The terms are not useless otherwise we wouldn't keep using them, but there are limits to how exact or precise they can be. But when working on a set, they get used all the time -- "let's hang a 2K zip over there as her backlight... I need a 4'x4' bounce over here for some fill... I want to key her soft from that window, etc." But it is certainly possible to avoid using the terms if you want to.

But sometimes you find yourself using the terms partly to describe intent -- for example, a bounce fill is likely to be less intense than a bounce key, so if you say that the bounce is for some fill, a Gaffer is less likely to be thinking that you'll want a 10K for it, instead of a Tweenie.
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