Lighting for Green Screen

K

Kugar13

Well-known member
Hey,

I watched a video that said when lighting for green screen use soft lights on the talent.

Here comes the ignorant question.... what criteria makes a light a soft light? I know diffusors and such can soften a light, but what about the light itself makes it soft? The color temp, type, etc.

Thanks everyone!
 
A softlight just has an optics system that prevents light being emitted from a point source. Worst culprits are any optics system that uses no reflector and a very small (length wise) filament. A spherical or elliptical reflector will boost light output but introduce a small and detectable blurring or softening of the beam. However, stick a finger in front of the lens and a larger version will be projected on the surface the light falls onto. If you increase the length of the fillament - as in linear lamps used in redheads or floodlights, and the finger test shows that in one plane, the shadow is not so pronounced, but in the other, it is still quite prominent. A lense with concentric circles - the common Fresnel lens also has a softening effect, as each ring is in effect a separate lense, and as these are spread out across the diameter, each one helps to soften the individual shadows. You still get a dark patch, but if you wave a finger a few inches in front of the lens, you won't see a clearly defined finger shadow. true softlights have designs that have hardly any direct an parallel light emerging from the front. The old studio types often had a 300mm tubular lamp (or two) in the bottom, which bounced light off a polished reflector to emerge from the front. These then had a really good intensity, but the finger test had little impact at all.

Putting a piece of heavy frost/diffuser/spun in front of an open face fixture, such as a redhead works as a softlight as the direct light from the lamp illuminates the large sheet, and this big lightsource then illuminates the subject - very soft light. White umbrellas use the same technique.

Colour has no impact on the 'quality' of light. The design of some hard sources allows a gobo - usually a small thin sheet of metal with a pattern cut in it to be put at the focal point inside the fixture - then you can project patterns of even logos. A softlight source uses a completely different optical system and cannot do this kind of thing at all.

Don't mistake the focus facility on a hardlight source for a magic 'turn into soft source' feature. It will soften up the edges, blurring them - but it's still hard. Fresnel lensed sources, even though quite soft, are technically still hard lights (although a different optical system, so can't use gobos). Real softlights are almost incapable of making shadows. Fresnels are soft hardlights, and profiles (ellipsoidals - in US parlance) are true hardlights.

Complex, isn't it?
 
Thank you!

Thank you!

Very complex indeed, yet you describe it so well! I can't thank you enough Paulears for taking the time to put together such a thoughful and detailed response. VERY informative and easy to follow.

If you don't mind me asking. Are there any soft lights you prefer to use for the sole purpose of interviews?

Thanks!


paulears said:
A softlight just has an optics system that prevents light being emitted from a point source. Worst culprits are any optics system that uses no reflector and a very small (length wise) filament. A spherical or elliptical reflector will boost light output but introduce a small and detectable blurring or softening of the beam. However, stick a finger in front of the lens and a larger version will be projected on the surface the light falls onto. If you increase the length of the fillament - as in linear lamps used in redheads or floodlights, and the finger test shows that in one plane, the shadow is not so pronounced, but in the other, it is still quite prominent. A lense with concentric circles - the common Fresnel lens also has a softening effect, as each ring is in effect a separate lense, and as these are spread out across the diameter, each one helps to soften the individual shadows. You still get a dark patch, but if you wave a finger a few inches in front of the lens, you won't see a clearly defined finger shadow. true softlights have designs that have hardly any direct an parallel light emerging from the front. The old studio types often had a 300mm tubular lamp (or two) in the bottom, which bounced light off a polished reflector to emerge from the front. These then had a really good intensity, but the finger test had little impact at all.

Putting a piece of heavy frost/diffuser/spun in front of an open face fixture, such as a redhead works as a softlight as the direct light from the lamp illuminates the large sheet, and this big lightsource then illuminates the subject - very soft light. White umbrellas use the same technique.

Colour has no impact on the 'quality' of light. The design of some hard sources allows a gobo - usually a small thin sheet of metal with a pattern cut in it to be put at the focal point inside the fixture - then you can project patterns of even logos. A softlight source uses a completely different optical system and cannot do this kind of thing at all.

Don't mistake the focus facility on a hardlight source for a magic 'turn into soft source' feature. It will soften up the edges, blurring them - but it's still hard. Fresnel lensed sources, even though quite soft, are technically still hard lights (although a different optical system, so can't use gobos). Real softlights are almost incapable of making shadows. Fresnels are soft hardlights, and profiles (ellipsoidals - in US parlance) are true hardlights.

Complex, isn't it?
Click to expand...
 
An explanation of hard vs. soft is just that the larger the surface emanating light source, the softer it will be.

As far as what you use for lighting green screen, its usually in two layers. Lighting for the screen itself and lighting for the subject in front of the screen. Lighting on the screen should be soft, flat and even. Fluorescent which is a great soft source makes good green screen lighting. As far as what you use on the talent, it can be anything that is appropriate for the background your are keying. For example, lets say the background plate (what you'll replace the green screen with in keying) would be a scene late in the day where the sun is low in the sky and you have a very hard light look of a certain color. You'd want to match whats going on in the background with how you light the subject. So you'd need a hard light to accomplish that, gelled appropriately to match the sunlight in the background scene. That sells the key better and helps make the subject look like they are really there so to speak.

You could also light with soft and even lighting for the foreground as well if thats what you need for the effect on the subject. You may still find yourself wanting to use a back / rim / hairlight of some kind though to help with definition of the edges of the person.

Hard lights are like fresnels or pars with a point light source inside. They might have a lens but some open faced lights don't have.

Soft lights are like fluorescents or some other source thats behind a large diffusion frame like silk (softbox is a common form for that).
 
Try out some Chinese ball lanterns over standard lamps. They aren't directional, but otherwise work very well for soft lighting. My favorite choice by far, although it's a bit extreme on the softness for most applications.
 
For lighting the green screen, Kino makes bulbs that have a green tint and deliver a soft, even light across the screen. It is also makes the green very vibrant and easy to key. Just watch out for green spill on your talent/object!
 
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