In the age of digital – light meters have, for the most part, lost popularity with photographers. With digital cameras it is easy enough to just take a photo, review the image immediately, and adjust your exposure as necessary. However, If you want to take the guess work out of getting perfect exposure then an incident light meter may be for you.
But my camera already has a light meter built-in!
True, all digital SLRs have a built in “reflective” light meter. However these meters can be unreliable under difficult lighting situations. Handheld incident light meters are much better at judging the light in the scene and rendering the proper exposure values.
Reflective vs. Incident metering:
In reflective metering the light reflected from the scene into the camera is recorded and compared against a standard value. In most cases this is 18% gray. This is fine when shooting an evenly lit scene made up of mostly middle tones but, is problematic when shooting scenes made up of mainly bright or dark values. To see this problem first hand try taking a picture of something pure white filling a majority of the frame. If you meter the image to ‘0’ the white object will apear gray in the final image.
Incident metering works by holding the meter up to the subject (meter’s sensor facing the camera) and taking a reading of the light falling onto the subject. Since the meter is recording the actual light hitting the subject rather than light being reflected, the meter produces a much more accurate reading.
Light meters can be expensive. Digital light meters like the Sekonic LITEMASTER PRO can cost up to $400. You can save some money however, by purchasing older analog light meters rather than their more expensive digital counterparts.
Analog light meters generally have a needle that points to zero when the proper exposure has been reached whereas digital light meters output the proper exposure directly to the screen.
Adorama frequently has used analog light meters in-stock for under $100. I have the Gossen Luna-Pro which I think is one of the best light meters for under $100 USD. See my tutorial on the Gossen Luna-Pro
So.. should you buy a light meter?
Like most things in life it depends… It is completely possible to get proper exposure without the use of an external light meter however, having a light meter in your bag can really come in handy when faced with a difficult lighting situation, or when the light has changed and you just want a quick reading of the light on the subject.