Taking a meter reading of the light that is in your shot can be the difference between an under/over exposed shot and one which is just right. I am not an expert on this subject, so rather than trying to write a tutorial I have found a selection of great articles from around the internet for your reference…
How do you meter a sunset? Or a flag backlit by the sun? Or a very dark-skinned subject? Or any other “tricky” exposure situation?
One way is to point your camera with its built-in light meter toward the subject…and pray a lot. The exposure you get may be right on the money, but it may be way off too. There’s got to be a better way. And there is! In a “simple” lighting situation – for example, a portrait of your friend taken outdoors under the shade of a tree – the traditional aim-your camera-and-trust-the-meter method usually works just fine. But when the lighting is more complex, you often need to use a different method to get the right exposure…….
In order to correctly expose your film or digital CCD there are two variables that must be identified: average reflectance and average light. Unless you have some good reason to meter for other than these two averages, stick meticulously to the method outlined below. This article deals with reflected light readings. This is the type of light reading taken with an in camera light meter or a hand held meter which is pointed toward the subject. This article does not deal with incident light readings which are a measure of the light falling on the subject….
A light meter does one thing. It tells you what the correct exposure is for 13% Gray. This is approximately the tonality of green grass or concrete. The meters that are built into almost all cameras today are reflective meters. This means that they are measuring the light being reflected off the subject. This is a convenient way to determine proper exposure but there are potential problems because grass and concrete usually aren’t our main subjects….
Imagine an exposure computer so advanced that it uses your eyes as a sensor. The processing unit is as powerful as your brain. The computer is accurate over a light range from reflected starlight through the light produced in a hydrogen fusion reaction. This computer weighs nothing and operates without batteries. It comes with instructions to allow you to implant the capabilities of the computer directly into your own memory so you can accurately judge a correct exposure by simply looking at the type of light that the subject is in. You are using this computer right now!
A light meter uses a photocell to measure the amount of light falling upon a subject (ambient light) or reflected from a subject (reflective light). Almost all modern cameras are equipped with some form of light meter (usually reflective)…..