Measuring Light Levels

Now that we have set our camera speed and shutter angle, decided on an f-stop to light for, chosen a film speed, determined how much depth of field we need, and selected a lens, we need to know how much light is actually on the set right now. In order to gather this all-important piece of information, we need a light meter.

If you have ever taken pictures, you are probably familiar with what a light meter does. It measures the available light, then tells you what settings to use on your camera. In some consumer cameras, it doesn't bother you with this information; it just goes ahead and sets the camera for you.

Filters are attached with C-47S.

In order to get an accurate reading, the DP must tell the light meter what film speed, shutter angle, and camera speed she is using. Then, based on that information, the light meter will come up with the proper f-stop. If the DP has a particular f-stop she wants to use, the gaffer just keeps adding light to the set until the light meter comes up with that f-stop.

There are two types of light meters in common usage: the incident meter and the spot meter.

The Incident Meter

Most of the time, the DP will use a meter that tells him the general level of light on the set. An incident meter measures the average amount of light that is falling on the face of a flat disk. As is, it only measures light coming from the front, but with the addition of a hemispherical light collector, which is a fancy name for something that looks like half of a ping-pong ball, the meter will collect light from above, below, and the sides. By holding this meter up in front of an actor's face, the DP can measure how much light is hitting the actor. The meter will read out an f-stop number which, when applied to the camera, will guarantee a proper exposure.

The DP usually wants to know more than just how much light is hitting the actor from the front. He may want to know how much light is coming from the side alone, or from the back. In this case, he may cup his hand over the light meter to shield it from one or more lights. The meter will give him an f-stop reading on those lights alone. He probably won't set the lens to that number—it just tells him how much brighter or dimmer those lights are than the front lights. This is important information when determining contrast ratio (something we will get to in a moment).

The Spot Meter

Whereas the incident meter tells the DP the overall light level, the spot meter tells her how much light is coming from one specific area. The spot meter has a viewfinder like a camera. The DP points the meter at a specific thing on the set and uses the viewfinder like a gun sight. The meter reads out how much light is reflecting off that thing. She may want to assure herself that there really is enough light on an actor's face. She may want to check a bright object in the frame to see if it needs to be toned down. She may want to check if an object in shadow will be visible at all. The spot meter can sight on a very narrow area, so a DP can get very specific information about how much light is reflected off a specific object or person.

One key difference between the incident and spot meters is that the incident meter is pointed at the lights—that is, it almost always is reading how much light is hitting a subject. The spot meter, on the other hand, generally reads how much light is reflecting off the subject.

Digital Cameras For Beginners

Digital Cameras For Beginners

Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.

Get My Free Ebook

Post a comment