To dim, or not to dim

[David Desio]

Hey all,

I have a question about when to use a dimmer on a light and whether this will affect the color temperature.

So here it is: When shooting on green screen (or any practical location) is it easier to just dim the light to slow it down, or should I be using scrims, silks, etc; to preserve the color temp?

 

Thanks,

Dave

[Michael Collier]

Dimmers always change the color tempature of any tungsten unit. No way around that. If you dim the lights that light the greenscreen, it will introduce more value in the red channel and the key won't be as clean. Now if your talking about light that only hits the subject and not the green, then its fine, it will warm your subject and your key will be easy. Otherwise avoid dimming. Put a scrim in there or light diffusion to control output.

 

When I have too many scrims (any more than two usually) I find a frame of opal works to knock down the light without softening it too much. Although if you already have two doubles or a single and a double, you and your gaffer might want to talk about switching the unit altogether, since your so far off exposure.

[David Desio]

Thanks Micheal. I figured it did change the color temp but just wanted to be sure. I guess with the warming effect, for video it would also have a little to do with what type of light and perhaps the intensity of the light when setting the white balance.

 

Dave

[Tim Pipher]

Good question Dave and I think I know why you asked it (great working with you last week, by the way).

 

From Michael's answer, I think the conclusion is what I had in mind -- don't dim the fluorescents that light my green screen cyclorama, but dim away as necessary on the lighting for the talent.

 

I'm not sure if we did it on our recent shoot, but a good way to do things is to turn off the cyc lights while lighting the talent to make sure we're lighting both the talent and the cyc optimally.

[Don Sommers]

I've been using KinoFlo Divas (4 light bank - http://www.kinoflo.com/Lighting%20Fixtures.../Diva-Lite.htm).

 

You can dim them while retaining colour temp ... you can switch off 2 of the 4 lights (I have the 4 lite versions) .... you can change the tubes for daylight or tungsten(colour temp) .... and, they run cool (which has been REALLY important in smaller rooms).

 

Only issue is they cost more than fresnels ..... but, I luv 'em .. worth every penny in my opinion.

 

Another option I've used (instead of scrims) is Rosco Gels (www.rosco.com). Using either specific (or layered) white semi-opaque gels cuts the light and adds a bit of the softbox effect as well.

[Hal Smith]

If enough interest is shown, I'll run a series of color temperature versus dimming percent tests with some lights that I own with my Minolta Colormeter II that is in certified calibration. I'll run a 750 watt Source Four ellipsoidal, 1kW Strand fresnel, and 5kW senior. My dimming equipment is professional quality Strand and I'll measure voltage with a Fluke 87III.

 

It will take me a couple of weeks to get around to the tests, my client's are all scared I'm going to retire and working me to death on projects. Who wants to retire when the money's good, the clients are good people, and the work's usually interesting? But it sure helps to keep them guessing.

[David Desio]

If enough interest is shown, I'll run a series of color temperature versus dimming percent tests with some lights that I own with my Minolta Colormeter II that is in certified calibration. I'll run a 750 watt Source Four ellipsoidal, 1kW Strand fresnel, and 5kW senior. My dimming equipment is professional quality Strand and I'll measure voltage with a Fluke 87III.

 

It will take me a couple of weeks to get around to the tests, my client's are all scared I'm going to retire and working me to death on projects. Who wants to retire when the money's good, the clients are good people, and the work's usually interesting? But it sure helps to keep them guessing.

 

 

That would be fantastic and very helpful. As for when to and when not to, I guess its up to the question of whether or not the subject calls for a warm look. Personally I have not been much of a fan of the look of the dimmed light on a subject's face but that's just preference and not law and new things are always fun to try. I'll be looking for those results, thanks :)

[Hal Smith]

That would be fantastic and very helpful. As for when to and when not to, I guess its up to the question of whether or not the subject calls for a warm look. Personally I have not been much of a fan of the look of the dimmed light on a subject's face but that's just preference and not law and new things are always fun to try. I'll be looking for those results, thanks :)

I'll do it. If anyone has a particular fixture they'd like characterized PM me and arrange to ship it to me. I can handle incandescents to 5kW with my dimming gear.