Advanced Light Measurement: Key Concepts
Photographers know that they need to be worried about the effect of light on their photographs and learn how to take a light measurement. But, there's more to light measurements than simply avoiding the mid-day. Users need to understand how light is reflected, how light falls on a subject and how to effectively use meters.
Step 1: Understanding Falling and Reflected Light
Before even stepping into how to measure light, photographers need to know how light exposure is measured. Light is either measured as it is reflected from an object or by how it falls on it. When a photographer is trying to measure reflected light, he is taking reflected light measurements. The second type is known as incident light.
Reflected light measurements are often not enough for most photographers. The reflected light measurements only indicate how much a reflective surface could be, not how reflective it really is. For example, even certain blacks can reflective, but a reflective light measurement wouldn't really take the black object into account. A bright day can throw off the measurements.
Reflective light should still be kept to a minimum. For example, a photographer wouldn't want to use a flash on a glass since this would cause the flash to reflect off the glass and onto the lens. But, sometimes reflective light is necessary to illuminate shadows and lines.
Step 2: Getting Better Measurements with Incident Light
While the reflective light measures can be limited, incident light works better for most people. Photographers generally need to worry more about how much light is falling on a subject, rather than how much light may reflect off surrounding surfaces.
Incident light meters tend to be accurate than reflective light meters since they provide more information about how much exposure is actually needed. They are also more sensitive to light in the area.
Step 3: Types of Meters
Light meters basically come in three types: spot, incident and color. The spot meter is a type of reflective meter, and it only measures the amount of reflective light in one section. For example, it could be used to measure how much light is on the White House Press Secretary. This meter can also be set up at different distances from the camera in order to obtain better readings on flash reach.
The incident meter was discussed previously, but it helps determine how much flash is needed based on how much light is falling on the subject. For example, if there is enough ambient light in the room to adequately light the subject, then there is no need to use a flash at all. One such incident meter is the Spectra Cine. This meter can be positioned in the same place as where the subject will be seated. Then, it will give a reading of all the light in that area.
Color meters are a little different than the previous two. As opposed to measuring just light, it also measures the color temperature of the light providers in the area. It will then provide the photographer with recommendations on which type of filters will work best to balance out the colors.