What is a light meter?
In simple words, a light meter is a device and a technology used to help the camera and the photographer to expose the scene correctly by calculating the ideal camera settings to click the desired frame. A light meter helps in detecting the required shutter speed, aperture and ISO settings which enables a photographer to click perfectly exposed shots.
It must have happed to you in your early days of photography, that some of your images came out to be over-exposed or under-exposed. No matter how talented a photographer is, one always needs to know how bright or dark the elements are in the frame he wishes to click. What a build-in camera light meter does is, it gathers the amount of light that enters the camera’s lens and then measures the intensity.
Image Courtesy: DigitalCameraWorld
But, there are situations when the camera light meter fails to assist you with correct camera setting. The reason behind this is that the light meter within the camera works in such a way that it reads all the elements in the frame and makes them into mid-gray, also known as 18% gray.
The 18%grey or mid-gray is basically a midpoint between the brightest highlight and the darkest shadow. As the camera light meter is not a human, it cannot detect which element in your frame you are willing to expose correctly. In a situation when you are not getting properly exposed photo even after using the light meter efficiently, you need to bring exposure compensation into play. Nowadays the DSLR cameras are equipped with multi-point light meters which a scattered all over to measure the intensity of light.
Types of light meters?
Built-in Camera Light Meters, also known as Reflected meters are used by aiming at the scene through the camera, and measure the amount of light that the subject in the scene reflects. Which means that these meters can only guess the amount of light hitting the subject.
The reflected meters are designed in such a manner that they are bound to see the subject as mid-gray, neither as white nor as black. This might work great in many situations, but many real life subjects have varied reflective qualities.
For better understanding, let’s take the case of two situations:
When the light falls on a white subject, it will reflect a lot of light, which will be read high by the camera light meter. In order to make it mid-grey, the camera will underexpose the scene.
Similarly, when the light falls on a black subject, very less amount will be reflected back, which will be read low and the camera will overexpose the scene.
Incident meters are used by aiming directly at the source of light and measures the amount of light falling directly on the subject, has nothing to do with the reflective quality of the subject. You can have better control of lighting in the scene you are planning to click by measuring all the light sources lighting up the various subjects in your scene.
An incident meter helps in achieving correct and accurate color tones and contrast by measuring the intensity of light falling on the subject, regardless of the reflective quality of the subject. Which means, the subject that is darker or lighter than grey will appear as it is and will not be compensated to mid-gray tone. Which concludes that the incident meters helps the photographer to accurately expose the scene for most of the lighting situations.
Which light meter would you prefer, incident light meter or the reflected light meter?