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Please clarify a basic lighting question for me!

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Josh Smith
Please clarify a basic lighting question for me!
on Sep 4, 2013 at 12:30:47 am

Hello everyone,

I'm fairly new to the video production game, and so far with regard to lighting, I've been using a set of three Redhead lights (all 800W) with dimmers. This seems to be absolutely ideal for using in a variety of situations as a 3-point system (key, fill and back lights), where I can use the dimmers to lessen the brightness of the lights according to the scene and the kind of effect I want to create.

Now, I'm looking to upgrade my lighting kit, and all the lights out there seem to NOT have dimmers. Am I missing something? My lights are VERY bright unless I dim them, so how to people get by without dimmers? How do they control the brightness of their lights? Do they even need to - do I not really need dimmers?! I am aware you can get lighting kits that have lights of different wattage (e.g. 1 x 150W, 1 x 300W, 1 x 650W etc.), but this is still very restrictive as far as I can see in terms of altering the look of the lighting - so am I doing it wrong...?

If someone can shed some light on the situation (pun intended...), that would be awesome.

Thanks,

Josh.


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Tom Miller
Re: Please clarify a basic lighting question for me!
on Sep 4, 2013 at 2:18:00 am

Hi Josh,

Very good questions. There are many ways to control the intensity of a light. Some also impact other qualities of the light, and some don't. Let's take a look at a few:

1) Dimming - Dimming a light does indeed reduce its intensity, but it also reduces its color temperature. In other words, the cost of dimming is that it goes warmer. This may be the effect you're after, but if not then you should use another method. BTW, I like dimming back lights as warmer back lights are often the effect I'm after anyway.

2) Diffusion - Pacing a diffusion gel (or soft box) over the light will reduce it's intensity, but it will also soften and spread the light. Again, this may not be the effect you're after.

3) Scrims - A scrim either placed in front of the light (e.g. as a net on a c-stand), or behind the barn door, is the most controlled way to reduce a light's intensity without impacting another quality of the light. For example, a double NET or scrim will reduce the light's intensity by 1 full stop. That means the light intensity is effectively cut in half. So you're 800 becomes a 400 just like that!

4) Distance - Moving the light farther from the subject reduces its intensity in a predictable way - perhaps obvious but an alternative that should be noted. Again it's about doubling and halving (funny thing about light and F-stops.)

We produced a whole DVD on this subject (called Lighting and Shooting Gorgeous Interviews) - which the COW sold until recently. We will be re-packaging it into a second edition shortly and make it available as a downloadable DVD or even an app.

Let me know if you have any questions about this, or if anything didn't make sense.

Tom Miller
Big Pictures, Denver
(303) 670-0625

http://www.BigPicturesMedia.com

"Award-Winning Camera Crews and Production Services in the Rocky Mountain West"


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Paddy Uglow
Re: Please clarify a basic lighting question for me!
on Sep 4, 2013 at 2:35:45 pm

Out of interest, does the colour temperature alter on LED panel lights when they're dimmed? Is the warming effect a property of light transmission or of the light bulb technology?
Thanks

Paddy, CreativeMedia.org.uk


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Bill Davis
Re: Please clarify a basic lighting question for me!
on Sep 12, 2013 at 5:20:08 am

[Paddy Uglow] "Out of interest, does the colour temperature alter on LED panel lights when they're dimmed? Is the warming effect a property of light transmission or of the light bulb technology?
Thanks

Paddy, CreativeMedia.org.uk"


Depends on the dimming technology you're using.

With older tungsten lamps, a traditional resistive dimmer like a rheostat would "starve" the filament of power and yes, the color temperature would drop as the light dims.

But in the modern electronic era, it's more likely that light manufactuers will use a switching power supply circuit to "pulse" the current going to the lamp at a very high rate os speed. Kinda like a super fast strobe. IF the light emitting unit can react fast enough (and LEDS are fast), then you can "dim" them by pulsing them in this fashion.

But that's not the end of the story. We're talking video here. Which means you have a frame rate in play. So it's possible in some circumstances to get pulsing rates and camera shutter rates that cause image problems.

For this reason, sometimes the traditional techniques like scrims, ND gels and just adding more light to subject distance to the mix will be a better solution than just always reaching for a dimmer.

Video is simple, huh? You just push the record button, swing the camera around at stuff and end up looking like a genius! ; )

Know someone who teaches video editing in elementary school, high school or college? Tell them to check out http://www.StartEditingNow.com - video editing curriculum complete with licensed practice content.


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