Jump to content


Photo

To dim, or not to dim


  • Please log in to reply
7 replies to this topic

#1 David Desio

David Desio
  • Basic Members
  • PipPipPip
  • 204 posts
  • Camera Operator
  • california, USA

Posted 01 August 2008 - 10:37 AM

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
  • 0

#2 Michael Collier

Michael Collier
  • Basic Members
  • PipPipPipPip
  • 1262 posts
  • Gaffer
  • Los Angeles, CA

Posted 01 August 2008 - 03:11 PM

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.
  • 0

#3 David Desio

David Desio
  • Basic Members
  • PipPipPip
  • 204 posts
  • Camera Operator
  • california, USA

Posted 01 August 2008 - 05:40 PM

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
  • 0

#4 Tim Pipher

Tim Pipher
  • Sustaining Members
  • 90 posts
  • Producer
  • Los Angeles (Burbank), CA

Posted 06 August 2008 - 04:01 PM

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.
  • 0

#5 Don Sommers

Don Sommers

    New

  • Basic Members
  • Pip
  • 9 posts
  • Other
  • Canada

Posted 10 August 2008 - 09:46 AM

I've been using KinoFlo Divas (4 light bank - http://www.kinoflo.c.../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.
  • 0

#6 Hal Smith

Hal Smith
  • Sustaining Members
  • 2280 posts
  • Cinematographer
  • OKC area

Posted 10 August 2008 - 12:39 PM

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.
  • 0

#7 David Desio

David Desio
  • Basic Members
  • PipPipPip
  • 204 posts
  • Camera Operator
  • california, USA

Posted 11 August 2008 - 10:07 AM

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 :)
  • 0

#8 Hal Smith

Hal Smith
  • Sustaining Members
  • 2280 posts
  • Cinematographer
  • OKC area

Posted 14 August 2008 - 03:24 AM

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.
  • 0


Visual Products

CineLab

Technodolly

Opal

Gamma Ray Digital Inc

Rig Wheels Passport

Broadcast Solutions Inc

Aerial Filmworks

Wooden Camera

CineTape

The Slider

Tai Audio

rebotnix Technologies

Abel Cine

Glidecam

Paralinx LLC

Metropolis Post

Ritter Battery

Willys Widgets

FJS International, LLC

Media Blackout - Custom Cables and AKS

Metropolis Post

Paralinx LLC

Ritter Battery

Broadcast Solutions Inc

Aerial Filmworks

Rig Wheels Passport

Opal

Media Blackout - Custom Cables and AKS

CineLab

The Slider

Abel Cine

Willys Widgets

Visual Products

Gamma Ray Digital Inc

Wooden Camera

Tai Audio

rebotnix Technologies

CineTape

Glidecam

FJS International, LLC

Technodolly