Photo Lesson: Lighting

Light can be a confusing subject. A lot of the terminology carries over from film technology, and different digital cameras use different sets of terms.

ISO (also called ASA or EI)
ISO is a measurement of your camera's sensor's sensitivity to light. Below are the ISO settings available on most digital cameras. As the number doubles, so does the light sensitivity. But as light sensitivity increases, the graininess ("digital noise") of an image increases.

• 100 - Very crisp image, very low light sensitivity
• 200
• 400 - Decent image clarity, decent light sensitivity.
• 800
• 1600 - Very noisy image, very high light sensitivity

I do not recommend shooting at an ISO above 400 unless the light conditions make it absolutely necessary. Most simple digital cameras severely decrease in image quality after ISO 400.

Shutter Speed
Very simply put, shutter speed is the amount of time your shutter is open. It is the amount of time the image sensor is taking in light. Shutter speed is measured in fractions of a second. For example, "60" actually represents 1/60 of a second. A slower shutter speed (lower number) takes in more light than a faster shutter speed (higher number).

When photographing a moving subject, a slow shutter speed will lead to motion blur:



A high shutter speed will produce a more "frozen" image:




Aperture (F-stops)
Aperture is, simply put, the size of the hole that lets in light when the shutter opens. F-stops are the basic measurement of aperture, but most point-and-shoot digital cameras do not use f-stops. If you wish to learn more about f-stops, please read this article.


What To Do If Your Camera Does Not Have Aperture/Shutter Speed Settings

Many point-and-shoot digital cameras do not allow you to control aperture and shutter speed. Instead, they combine the two into a single setting called "EV" (Exposure Value) or "Exp." In these settings you will see a readout somewhat like this:

< -2 . . 1 . . 0 . . 1 . . 2+ >

By default, the camera will be set to the midpoint 0. Pushing it up to 1 will double the amount of light. Pushing it to 2 will quadruple the light. Likewise, moving down to -1 will cut the light in half, and -2 will divide it by four.


White Balance
When your camera takes a picture, it compresses the raw data that the sensor receives into a jpeg file. When it does this, it decides what color in the image is white, and all of the other colors are decided in relation to the color white.

While it all light may appear to be the same color to the untrained eye, different light sources the sun, flouresent bubs, etc.) have different hues. White balance is used to make white objects appear white, and the other colors appear natural as a result.

You camera has several white balance settings, usually including Auto, Sunlight, Cloudy, Florescent, Flash, Custom (and often others). Automatic white balance is often inaccurate, so it is worth trying one of the other settings. Take a picture or two to see how the image turns out.

For the most accurate color, use Custom (Manual) white balance. This setting allows you to set the white balance based on on actual white object. To do so, place a white piece of paper directly in your light source. Point the camera at the paper and make sure it fills the frame (you should see nothing but white, and no shadow). Select the Custom/Manual white balance, and then hit "OK" (called "Func." on some cameras). You white balance will now be set perfectly for your lighting conditions. Remember: if the light changes at all, you will need to reset the white balance.

Supplementary Materials

• The Exposure Triangle (an explanation of the relationship between shutterspeed, ISO, and aperture)
• ISO Settings in Digital Photography
  
• Introduction to Aperture in Digital Photography
• Introduction to Shutter Speed in Digital Photography
  
• Introduction to White Balance
• Expressing Motion In Photography (This article discusses different uses of shutter speed to display motion)