What is the Film Plane Indicator that Odd Symbol on the Camera

Have you ever seen that small circle on your camera that appears to have a line drawn right down the center of it? If you’re wondering what the weird symbol on your camera is, it’s your film plane indicator and it actually has several uses. While the name of this helpful little object comes back from the days when filmmaking was a bit less advanced, the film plane indicator or focal plane indicator helps to direct you to the area that is exactly in line with your camera’s sensor.

What is the Film Plane Indicator For?

The circle symbol with the line through it that represents your film plane indicator is there to provide a visual reference for you that helps you to measure focus.

The actual focusing distances of your lens is measured from the surface of your camera sensor or film, not from the front of the lens or back of the lens as you may have thought. But what does this all mean?

In order to accurately measure focal distance of your lens, you need to know where to measure from. If it’s not from the front or back of the lens, then from where?

You measure from the film plane indicator!

How the Film Plane Indicator is Used

Photographers will probably not understand the film plane indicator and its uses, largely because it doesn’t really apply. However, for filmmakers, it’s an important concept to understand and a helpful feature for your camera.

Sometimes referred to as the sensor plane indicator, cinematographers use the film plane indicator to understand exact focus length from the camera sensor to the object in view.

This is important to understand as you learn how to understand the way the film plane varies in distance from the overall lens focal point. Different lenses can cause the focal point or length to change which is why you have this easy to see focal plane indicator.

The film plane indicator provides an understandable position of the camera sensor relative to the camera lens. This helps you to keep targeted measurement of focal length despite changing viewpoints or activities. 

When a focus puller places small focus hooks to one side of a tape measure in order to quickly gauge the overall distance from the camera to the objects being filmed, the goal is to bring the camera in focus.

The measurement that is captured is taken from the film plane to the subject on camera. This is why the film plane indicator is commonly used to help the cinematographer and focus puller to improve the area of critical focus on the set.