Controlling the light and mastering the exposure is the mantra for success as a photographer. Understanding the camera’s metering is akin to mastering the light & exposure. Getting to know how the camera reads the light and translates this information into shutter speed, aperture value and ISO is what determines the exposure; optimal exposure to be precise.In case of digital cameras, it is an in-built light meter that works as the brain behind the camera’s calculation for determining the shutter speed, ISO and aperture values for a particular scene. The in-built light meter takes the guesswork out of the field and enables you to get optimum exposure in almost all the cases when the camera is operating in auto and semi auto modes. I have personally experienced this neat camera trick of determining the exposure and would like to encourage you to test it out for yourself if you haven’t yet played around with it. Turn your camera to one of the semi-auto modes; aperture priority or shutter priority. Let’s take shutter priority for instance. Set the shutter speed to any arbitrary value say 1/30sec. and keep the ISO to ISO 100. Mount the camera on the tripod.
Now rotate the camera and make a note of the aperture values as the camera pans. The camera meters and automatically sets the appropriate aperture value depending upon the amount of light entering the lens. This explains the basic functionality of a light meter — the ability to determine the proper exposure (in terms of aperture f-number, shutter speed and ISO) for a photograph.
While the sophisticated digital beasts nowadays have in-built light meters, professional studio photographers still keep the external light meters handy. These hand-held light meters enable them to proficiently work in the manual mode and yet get the exposures that they want (and the final result as visualized by the client). The hand-held meters help them get the accurate exposures under various lighting conditions. But before looking at the how and why of the light meters, let’s start with what a light meter basically is….
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