A fair question these days is whether or not you still need a hand-held light meter? In the old days light meters in the camera were pretty simple. There was a needle over on the side and a center mark on the scale. The closer the needle was to the center mark, the better off you were. Cameras were “center weighted” which meant whatever you had in the center of the field of view was what the needle was registering.
That arrangement seems hopelessly primitive compared to today’s cameras that use sophisticated multi-point metering systems that sample many points inside a photograph and use that sample set to compute the optimum average exposure value.
Despite the difference in applied technology, the meters are still doing basically the same thing: Reading the light reflected off a subject and calculating an exposure value based on 18 percent gray. Why 18 percent gray? Because it turns out if you average all the values across a scene it all boils down to that figure.
When considering the decision of whether to get a light meter, it also helps to understand the difference between reflected light and incident light. Reflected light is what allows you to see anything. When you look at an object, your eyes are seeing the light reflected off the object to your eye. Incident light is measuring the light falling on the object, irrespective of what’s being reflected.
Light meters work by filtering the light through a dome that approximates an 18 percent gray card.
When incident light meters are most useful is when you’re working with strobes. You can remotely pop your flash setup and get an exact light reading at your subject. You can also take readings from multiple sides if you’re trying to set up a particular light ratio.
Having a decent light meter can be a great way to add consistency to your photography, by helping you dial in your starting settings. That saves a lot of time when working with expensive models. As often as you’re changing the light setup and moving around, a good light meter will be invaluable for working fast and changing setups.
A good light meter does not have to cost a lot of money. Here are a few good models for under $300.