Some light basics. It comes in colors. You can add/subtract light. You don’t really see light – what you see is light reflected. So let’s reflect on light for a while.
I just did a couple of workshops for STN, one on basic lighting. A prior post, Some Simple Lighting Tips, reviewed the basics of working with natural light. Daylight.
Today let’s look at artificial light. It comes in a couple of colors. When you’re talking light, you should know that it is measured in degrees Kelvin (after British Lord Kelvin). You may have noticed that sunsets are often a beautiful red or orange. Overcast days seem cool – bluish. Your perceptions are right on, but not totally. You run into a lot of different types of light every day, but your brain (like the auto-white in your camera) is constantly translating light so that you “see” colors consistantly, no matter what the light.
Try this. Set your camera/camcorder on manual white balance and set the white in bright sunlight. That will be our standard. Shoot about ten seconds of tape. Now shoot ten seconds of the following scenarios.
1. Starting at the low end – candle light. Candle light is at the low end of the spectrum…under 2000 degrees Kelvin. It is warm.
2. Rachett it up a bit and you have regular household lights at around 3000 degrees…brighter, but still with an orange cast.
3. Professional lights (quartz halogen) are up around 3500 degrees.
4. Flourescent lights are squirrely. They have a wide range (from tungsten to outdoors) and come in different colors as a result. You can get a warm white (close to regular household lights) or a cool white (more balanced to daylight). Some of the older or industrial lights cast a green shade.
5. Now we’re outdoors in direct sunlight again (5600).
6. Finally, open shade (7000 degrees).
Why all the concern about the color of light and temperature? Because if you are working in manual white balance mode (and yes, most pros do this except in emergencies), you have to know your light or your tape will look bad. This is especially true if you have to shoot under mixed light, like daylight and tungsten. Candlelight and flourescent. You have to make the decision about which type of light you want as your main source and which type of light you want to kill off.
Sometimes you may want to use mixed light as an effect. Often, when shooting an interview in an office, you encouter this scene. Large window with desk in front of it. The person sitting at the desk has their back to the window. You have to deal with this overwhelming backlight. (Why, I wonder, doesn’t the person in this wonderful office with the great view turn their desk around and enjoy the view?) First, I’ll be kind and give you an overcast day so the light levels between the indoors subject and outdoor scene don’t create an impossible situation (and there are ways to deal with this, but they aren’t easy or cheap.) Here are some solutions.
1. Go for the daylight look. Pop a dichoic filter over your (stand) light. Dichroics change the value of quartz lights from 3600 to daylight…more 5600. Background and subject are the same color.
2. Go for the mixed look. By simply using the (stand) light, you will have a warm subject and cool background. I don’t like this personally, but have used on occassion. (One time when the window looked out on a whitewashed brick wall – ugly. Lit the subject and backed up as much as I could, using tele lens…final shot of subject’s face with out-of-focus cool background.)
3. Not cheap/not easy. Have some gel that is large enough to cover the window – orange gel and probably a neutral density gel. Tape them in place, use your light kit and you once again have balance.
4. My solution 99% of the time in a situation like this is to simply explain the situation to the subject and ask them to move…generally to another location. The biggest problem in the above scenario is not really the color temperature, but rather the difference between the intensity of light hitting the subject’s face and what comes in over his or her shoulder. Hopefully by moving the location I’m back to dealing with one type of light again.
By the way, you can use reflectors in an artificial light situation. Great way to fill in those pesky shadows and better than nothing.
I’ll try to have some stills of posted over the weekend to compliment this.
For more details on degrees Kelvin and a pretty decent chart, check out 3drender.com.