What Is White Balance in a Camera?摄像头里的白平衡是什么意思

What Is White Balance in a Camera?

Anyone with a digital camera has probably heard the term white balance. In the days of film, photographers could not adjust white balance in their camera. Previously, photographers managed this by purchasing film based on the color temperature of light; either
film balanced for daylight or balanced for tungsten light. Today's digital cameras can automatically make these decisions, leaving the photographer more freedom and time to create images.

White Balance Defined

Have you ever taken a picture inside without flash and the picture looked orange? That's because the image wasn't properly white balanced. When a photograph has correct white balance, all objects in the scene have a neutral color tone. That means white
objects appear white, blues appear blue, greens appear green and grays appear gray. All cameras work to obtain a correct white balance regardless of lighting conditions. The science behind white balance starts with the color-temperature scale developed by
physicist William Kelvin.

Degrees Kelvin

The Kelvin scale measures the color temperature, or hue, of a specific light source. Daylight at sea level has an approximate color temperature of 5,500 to 6,500 degrees Kelvin. Under these daylight conditions, colors appear neutral. That is the goal of
the white balance setting in a camera. When the color temperature goes below 5,500 degrees Kelvin, colors start to contain more orange and yellow. Incandescent light bulbs (household lights) have a color temperature around 3,200 to 3,400 degrees Kelvin. This
lower color temperature results in an orange/yellow appearance on film. When the color temperature rises above 6,500 degrees Kelvin, colors appear more blue/purple. Photographs taken at high altitudes often exhibit this blue/purple colorcast. Flash units are
balanced to simulate daylight and typically have a color temperature of 5,600 degrees Kelvin.

Automatic White Balance

All digital cameras have an automatic white balance feature; some also have a manual white balance feature. Automatic white balance attempts to correctly balance a scene's color temperature regardless of the light sources available in the scene. For example,
fluorescent lights have a color temperature that emits a green colorcast. Automatic white balance attempts to correct this green colorcast and make objects in the scene appear normal. Cameras with manual white balance options allow the photographer to manually
adjust the camera's white balance settings in greater detail.

White Balance Challenges

Automatic white balance does a great job most of the time, but certain conditions can fool the camera's built-in technology. Scenes that have multiple light sources of different color temperatures often fool the camera's white balance sensors. These
scenes often require manual white balance adjustments. Another scenario that fools the camera occurs when a small subject is surrounded by a large expanse of color; for example, a child standing in front of a red barn. The large color expanse tricks the camera
into making a white balance adjustment to offset the red barn. The resulting image contains too much cyan, the opposite color of red.

How to Understand White Balance in Photography

Read more : http://www.ehow.com/how_2213324_understand-white-balance-photography.html

How to Understand White Balance in Photography

Most amateur photographers have experienced the frustration of digital images that come out with a blue or orange cast. Digital cameras rely on white balance to produce images with true color. While auto settings usually work well, adjusting the white balance
in your photography can lead to truer color in your final images

Instructions

1 Determine the type of light in the scene you are photographing. Indoor incandescent light tends to be more red or orange. Bright light outdoors, especially in snowy scenes, can tend toward blue tints. White balance settings in your camera will adjust for
this natural shift in colors.

2 Compose a test shot. Use the auto white balance feature.

3 Determine how your camera handled the white balance. Look at the whitest part of your image and check to see if it is truly white. If it looks blue or yellow, you should adjust the white balance.

4 Adjust your camera settings to the type of light you are experiencing. There are often settings for indoor light, bright outdoor light, candlelight, snow, beach and florescent light. High-end cameras may have additional settings. Select the setting that
matches your scene. This tells the camera how to shift the way it sees color to match the true color of what you are photographing.

5 Experiment with the RAW setting. Newer digital cameras and those designed for professional photographers allow you to shoot without any color correction or white balance settings at all. This can be particularly useful in shooting landscapes at dawn
and dusk. It also allows you to understand what your camera is doing when it is adjusting white balance.

Read more : http://www.ehow.com/info_8198740_white-balance-camera.html