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Please clarify a basic lighting question for me!

puremotion's picture
Last seen: 1 year 2 months ago
Joined: 06/13/2012 - 9:56pm

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.


rs170a's picture
Last seen: 16 hours 33 min ago
Joined: 03/07/2011 - 2:12pm

I'm guessing that you have separate dimmers as redheads don't come with them built in so just use those with whatever lights you buy. I've got 4 dimmers I use on a regular basis with my lowel kit. FYI, I had them custom made for me using commercial grade dimmers (1200 W. capacity) as standard home dimmers can be too noisy (from an electrical standpoint).

 

Mike


Rick Crampton's picture
Last seen: 5 months 1 week ago
Joined: 08/20/2009 - 1:08pm

" so am I doing it wrong...? "               That'd be MY guess. Pro's select their incandescent instrument's wattage based upon the amount of light they need, and by adjusting between " spot " and " flood ". Fine tuning is done by adjusting the distance from the instrument to the subject and/or the introduction of scrims. What happens to your color temperature when you use a dimmer? . . . . curious . . . .


VideoDog's picture
Last seen: 4 weeks 1 day ago
Joined: 01/07/2010 - 6:18pm

Hello Josh,

 

Rick asks an excellent question and I would like to hear from Mike as well.  What happens to the color temperature when you dim?  You may be aware that some videographers are strongly opposed to mixing color temperatures on a set because it can look funny and make color correcting or color grading more difficult in post.  If the lights you dim are not designed to hold their color temp through dimming, you could be putting 5400 degree light on one side of your subject and something much different on the other side as fill.  I now have some "Cool Lights" (both flourescent and LED) that have dimmers built in that are supposed to keep the color temperature the same from 10% to 100%.  That is a brand name and just so you know, I have no connection with the company. When ever possible, on a set, I eliminate all other light sources (including covering windows) and light with the same lights.  Like Rick said, scrims cut intensity.  So does the inverse square law of light.  If you move a light half the distance to your subject, it gets twice as strong.  A little distance goes a long way.  If I buy a light, I make sure the dimming function is designed into the unit and the color temp stays constant.  Another thing you want to consider is CRI or how faithfully colors are reproduced under certain lights.  I didn't believe it until I bought lights with a 93+ CRI and my jaw hit the floor when I saw skin tones from those lights.


Rick Crampton's picture
Last seen: 5 months 1 week ago
Joined: 08/20/2009 - 1:08pm

" Another thing you want to consider is CRI or how faithfully colors are reproduced under certain lights.  I didn't believe it until I bought lights with a 93+ CRI and my jaw hit the floor when I saw skin tones from those lights. "       Hard to beat a Joker Bug . . . . even tho they are a bit pricey


Bowens's picture
Last seen: 6 days 22 hours ago
Joined: 09/05/2013 - 1:18am

Hi Josh. Last year we launched our Limelite brand of continuous lighting for video and our new Pixel 300W 3-point tungsten lighting kit includes an in-line dimmer with each head. You also get 3 sets of barndoors, 3 lighting stands, a set of spare bulbs and a padded kit case - see http://www.limelite.us.com/index.php/tungsten-lighting/pixel-three-point... for more information. As others have already commented, please be aware that color temperature (CT) will shift as you use dimmers to vary light output, as CT is affected by the voltage changes employed to dim the lights. At full power our lights are 3200K, but this can vary by a few hundred degrees K as you dim the lights. Our barndoors feature handy gel clips, so it's worth carrying some CT gels to help balance lights under differing output conditions. You can also change the standard 300W bulbs for 3200K 150W bulbs to reduce output without affecting CT if you need to.


rs170a's picture
Last seen: 16 hours 33 min ago
Joined: 03/07/2011 - 2:12pm

As Bowens points out, colour temperature will vary with tungsten lights as you dim them. Take a look at a Kelvin scale shart and you'll see that it will get redder as you dim them.

As has already been mentioned, there are numerous ways to offset this by using scrims, diffusion material, distance, etc. and I've used all of these at various times.

If I don't have any of these at hand on a shoot, I will use dimmers and then do a white balance once I have things lit the way I want. If I'm adding any coloured gels to my lights, I do my white balance before I add the gel to my lights.

BTW, having a properly calibrated video monitor on set is a huge bonus as you can instantly see if what you trying to achieve is actually working.

 

Mike


dellwovideo's picture
Last seen: 2 weeks 21 hours ago
Joined: 05/20/2011 - 6:35pm

If you don't have dimmers (or a light meter), you can always use the inverse square law to roughly calculate relative illumination by distance from the light to the subject.

 

When you double the distance, you reduce the illumination by a factor of 4. 10 feet to 20 feet equals 1/4 the light.

 

In order to reduce the illumination by a factor of 2, increase the distance by a factor of 1.4. (The square root of 2.) 10 feet to 14 feet equals half the light.

 

http://en.wikipedia.org/wiki/Inverse-square_law

 

It's all a complicated way of saying if you don't have dimmers, move your lights.  :-)