Archive for the ‘Light’ Category

What’s All This Light “Temperature” Stuff?

Friday, May 15th, 2009

Videographer Light Color TemperatureIn digital imaging there is a fundamental practice all videographers must contend with–White Balance. Without an initial white balance, white will not be white and an overall hue will pervade the picture. To obtain a white balance the videographer places a white source in front of the camera and then tells the camera that what it is currently looking at is white.

The astute reader is probably now asking, “Why isn’t white always white? What’s the big deal?” Here is another example of why human imaging capabilities far surpass electronic imaging technology of today. Suppose you were to look at a white table cloth in a dance lounge where the DJ had a lot of multi-colored lighting flooding the dance floor. Would the white table cloth still look white to you? Probably not. The exact same limitation exists for electronic imaging except that it is far more narrow. Outdoor light is a different color or temperature than indoor tungsten light. The human brain is able to process the difference and white still looks white to you whether you are outside or indoors. Electronic imaging technology has not come that far yet. Recent technology developments have enabled an auto white balance capability commonly used in consumer grade cameras which is not too bad at white balancing. However, the pro videographer cannot settle for such white balancing and usually will want to manually capture a white balance before each shot.

There are two fundamental conditions that are commonly light balanced for: outdoor and indoor. While each has variations within, generally speaking outdoor light is 5700K (degrees Kelvin) and indoor tungsten lighting is 3200K. With a camera white balanced for outdoor imaging white will have a yellow hue when captured indoors. An indoor white balanced camera will show white outdoors with a bluish hue.

A Special Stage Lighting Consideration

Thursday, April 30th, 2009

bubsptltWhen capturing video from staged events it is common to observe concentrated directed light from overhead spotlighting installed in the theater ceiling. This lighting, by design, usually lands on subjects on the stage that we are capturing to video. We are then forced to choose between a properly lit subject and an overall well lit stage. The former is always the winning choice but what this means is that the rest of the stage in the video takes on a shadow-like appearance.

For weddings we have found that it is better to have an evenly lit overall appearance so we ask the site staff to lower the overhead lights. You would think that we would crave any lighting we could get but this sort of lighting is counter-productive to good imaging. The surrounding ambient lighting is more than sufficient to allow us to capture fabulous video.

 

For staged events where almost all of the activity to be captured happens at a specific location such as a graduation ceremony, we elect to leave the overhead lighting unchanged. Intense light on the subject allows us to capture vivid color and skin tones that pop and look extremely pleasant to the video viewer. The background surrounding the speaker takes on a darker tone that corresponds with its lesser significance.

Auxiliary Lighting

Thursday, April 23rd, 2009

studiolightingLighting used in video capture depends on a variety of factors. These include the limitation for practical reasons and the necessity to use lighting.

 

First, a brief discussion of what lighting does for video imaging is presented. Any imaging system requires a minimum amount of light to produce optimum results including the human eye. Optimum results are usually interpreted to mean vibrant colors and fine detail of the image. When some of that minimum light is discarded, the colors begin to fade while fine detail is still present. Taking away still more light, the imaging electronics begin to compensate by amplifying (increasing the video gain) of the light that it is working with. Increasing the gain a slight amount is usually not noticeable in the results although significantly increased gain will result in graininess or loss of some minor fine detail in the image.

 

I would identify four different grades of available light:

  • Excellent: colors will be vibrant and pop, detail will be optimum. Usually this is only attainable indoors with auxiliary lighting or outdoors without.
  • Good: colors will look very nice with fine detail. This is usually attainable indoors with no auxiliary lighting.
  • Poor: colors will be bland and video gain may increase slightly.
  • Insufficient: camera gain will max out causing noticeable graininess in the image. Usually halving the shutter speed improves these results dramatically while the resulting motion blur is almost imperceptible. Tight zooms are prohibited.

The Practical Limitation Preventing use of Auxiliary Lighting

There are times when it is not practical to use portable studio lighting such as at a wedding ceremony. This is not only because it would be a distraction but because the distances usually involved between the camcorder and subjects are large making any supplemental lighting ineffective. Fortunately, most sanctuaries have sufficient ambient light for good imaging as defined by the category “good” above.

 

We do, however, routinely use on-camera lighting at wedding receptions. Please ask to see samples showing how vibrant colors become in even dimly lit dance floors.

 

Here is a curious note: Some sanctuaries have large sky lights letting in a flood of exterior lighting. When this lighting mixes with the indoor ceiling lighting, a color mis-match occurs which is MURDER for video imaging. The temperature of outdoor lighting is 5700K while indoor lighting is 3200K. Video imaging can deal with one or the other but not both simultaneously. The usual solution for these cases is to have the site manager turn off the indoor lighting even though it gives us less light to work with.

 

The Necessity to use Auxiliary Lighting

There also times when it would be foolish not to use studio lighting such at a studio interview. Still, there are other times when acceptable results are possible without lighting but the client wants stunning imaging. What it really comes down to is a trade-off between operational conditions and what level of results are required.