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Old September 1st, 2008, 06:05 AM   #1
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Some basic help on using gels

I'm a little bit lost on when to use gels and when to do a white balance...

I understand that using a blue gel over my lights in a room with day light coming in will match the temperatures. Alternatively covering the window with an orange gel will achieve the same effect. But many of my interviews tend to be in a room with day light, a ceiling light of some sort and my own lights. In that instance is there any point in my having the blue gel/orange gel on if I'm gonna have to do a white balance anyway? Or will that still help with the temperature somehow?

Cheers, Neil
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Old September 1st, 2008, 06:18 AM   #2
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Mixing color temperatures doesn't work well with white balance and only confuses it and makes for a mish mash terrible looking effect especially when fluorescent, HMI or LED and other kinds of discharge lighting are involved. Its best to match everything as much as possible to the same color temperature or at least as close as you can get. And controlling what you can't gel too easily will help. For instance, with daylight coming in the window, you can block out the window with duvetyne or whatever and just use tungsten. Or you can leave the daylight coming in and gel your tungsten with CTB to daylight color. Flos overhead are a whole different matter and its tough to control those in a big office setting.

You can mix color temperatures sometimes but its best to do it after white balance and you can get interesting but exaggerated effects that way--and that is a whole other story.
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Old September 1st, 2008, 09:09 AM   #3
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If you are shooting ENG and just running and gunning you may not have time to set up proper lighting. But otherwise, I have never run into a situation where I couldn't turn the room lights off. I am not saying that it doesn't happen, but I have never run into that problem before.
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Old September 1st, 2008, 12:51 PM   #4
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Thanks for both replies. I do shoot mainly ENG and sport stuff and there are some times when I can't control the light. In those instances I've always put the blue gel on my lights, more out of habit than anything I guess. I'm wondering whether I'm wasting my time by doing that?
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Old September 1st, 2008, 01:00 PM   #5
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The fewer dissimilar colour temperature light sources in the shot, the better.

The key is to white balance on a white object with either:
a. the predominant light source in the room falling upon it; or
b. the light source that is falling upon the most important subject in the room (where colour accuracy will be most noticeable) ie. someone's face

I keep a daylight dichroic filter AND a diffuser permanently mounted in swing away holders on my Anton Bauer on camera light. Under daylight fluoros or in a room lit mainly by windows (and a mix of fluoros?), I'll "kick in" the dichroic filter. If I'm in a person's study, lit by tungsten lamps, I'll swing in the diffuser and leave the dichroic out.

Make sure to white balance AFTER making the light on/light off or blue gel on/blue gel off decision.

Hope this helps.
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Old September 2nd, 2008, 11:57 AM   #6
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Blue gels are a pain on a tungsten fixture, because they tend to eat so much light. That's why a couple of 400 par HMI lights can really be your friend...but they are very blinkin' expensive!

Sometimes I'll play mix and match. If you can put a light blue gel on the tungsten light, and get the camera to balance to about 4300K, then the windows aren't too blue, and any lights in the background--lamps or ceiling fixtures--aren't too warm.

Flourescents can be a grab bag. They tend to skew higher in color temperature, but often have a green cast. In an office environment with unavoidable overheads like that, I generally try to add some cool light, and then balance for the overall ambient light.
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Old September 2nd, 2008, 12:42 PM   #7
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Neil, if you don't use CTB on your tungsten lights when there's daylight coming in, and if you white balance to the tungsten light on your subject, then all areas where daylight hit will be too blue. As others pointed out, the idea is to get all the light sources as close to the same color temperature as possible.

Lots of office fluorescents seem to be around 4500K, about halfway between tungsten and daylight. In those cases you can use 1/2 CTB instead of full and get close enough. In fact, I've often done that to deliberately warm up the subject from the background. Also, 1/2 doesn't eat up as much of your light as full. With lower cost HMIs out there, LEDs and daylight fluorescents, it's easier now to come up with daylight sources instead of gel.
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Old September 2nd, 2008, 12:47 PM   #8
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Quote:
Originally Posted by Bill Ward View Post
...Sometimes I'll play mix and match. If you can put a light blue gel on the tungsten light, and get the camera to balance to about 4300K, then the windows aren't too blue, and any lights in the background--lamps or ceiling fixtures--aren't too warm...
I'm with Bill on this - I carry full, 3/4 and 1/2 CTB, they're inexpensive. I try to use 3/4 as the match for front lighting, and 1/2 whenever possible. It works out well, giving much more punch on the little lights I carry.
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Old September 15th, 2008, 02:59 PM   #9
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Mixed lighting can be nice in a run'n'gun situation, I've done it just today. There was some daylight (dark, overcast) coming in from the windows and some kind-of daylight from some fluo tubes from near the window. I used both as an edge/background light, I set the camera to tungsten preset, put a sheet of cosmetic rouge on my 50W tungsten on-camera light and shot the interview. The result was a nice warm skin tone with a cool ~110 edge light and a blueish tint on the background. Far from the perfect interview lighting, but nice for a 1 minute setup.

When you cover the windows with Full,3/4 or even only 1/2 CTO then you can use your tungsten fixtures without gelling and still get relatively the same color temperature. You gain lumens from your fixtures by darkening the daylight and not gelling the lamps.
However in eng you can always try to use un-gelled lamps with un-gelled daylight - although you have to seperate the daylight from the lamps then (like using daylight for the background/edge light and the tungsten for key/fill or the other way round - just like what I said before)
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Old September 16th, 2008, 09:52 PM   #10
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What if the lamp/light is in the shot?

In a situation where the shot involves multiple types of light sources, daylight, tungsten lamp, fluorescent, etc. and these elements are visible in the shot, then isn't the only option to change the bulbs in those lamps to the same or similar temps.? For instance using daylight balanced florescent bulbs and daylight balanced tungsten bulbs? There are such things right?
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Old September 16th, 2008, 10:01 PM   #11
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There's no such thing as a daylight tungsten bulb. You'd have to go with an HMI light, or use CTB gel.
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Old September 17th, 2008, 10:52 AM   #12
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Most of the answer is in all those responses so far.
Here's my MO:
- identify the color temp of the surrounding ambient light
- match my on-cameras light or stand lights to the ambient or shift towards slight warmth if shooting skin tones.
EXAMPLE SCENARIO:
ENG/ SPORTS outside. Interview of player or coach
Ambient = 5,500K Daylight on overcast day.
On Camera = 5,500K LED fixture (LED-Z for example)
Gel Filtration required? = 1/8-1/4 CTO on the light to warm up the face.
Procedure:
1- FIRST WB to a white card in the ambient light. This locks your camera in to yield neutral and clean whites in the background
2- Turn on your light with the 1/8-1/4 CTO ( Amber)
3- Expose for the correct skin tone
4- Shoot
Result is a healthy warm skin tone and perfectly White Balanced background.
For indoor shots with incandescent or fluorescent lights I basically do the same thing but obviously will have to add a Full CTO or FULL FLD Fluorescent Filter to my LED camera light. Then, if shooting interviews, I'll add that 1/8CTO to boost the warmth.

Lighting is an art and a whole specialty within film making. Understanding how WB affects your footage in relation to your supplementary illumination gets you the punchy shots you desire.

Whatever you do, DO NOT use those white balancing diffusers in front of the lens.
DO use a professional White card for White balancing your largest and least controllable light source .
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Old September 17th, 2008, 11:29 AM   #13
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Originally Posted by M. Paul El-Darwish View Post
Ambient = 5,500K Daylight on overcast day.
Keep in mind that a true 5500K reading (regardless of what the camera's circuitry may tell you) is not overcast at all. It is bright direct sun. Overcast starts in the low to mid 6000K and goes up over 10000K.
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Old September 18th, 2008, 11:20 AM   #14
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Respectfully, I've not ever measured Midday overcast at anything above 5,500 K. Clear Skylight jumps above 6,000K it is BLUE after all ;)

Quote:
Originally Posted by Shaun Roemich View Post
Keep in mind that a true 5500K reading (regardless of what the camera's circuitry may tell you) is not overcast at all. It is bright direct sun. Overcast starts in the low to mid 6000K and goes up over 10000K.
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Old September 18th, 2008, 04:49 PM   #15
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Quote:
Originally Posted by Damian Vines View Post
In a situation where the shot involves multiple types of light sources, daylight, tungsten lamp, fluorescent, etc. and these elements are visible in the shot, then isn't the only option to change the bulbs in those lamps to the same or similar temps.? For instance using daylight balanced florescent bulbs and daylight balanced tungsten bulbs? There are such things right?
If daylight is your main illuminant, you could try using daylight balanced compact flos in table lamps. But here's the thing... you sometimes have to 'create' your background in these situations. Believe me, a good DP won't let multiple color temp light sources in the shot if they can't be gelled or otherwise controlled.

-gb-
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