Basics of Focal Length

The term focal length gets thrown around a lot without a clear understanding of what it is exactly and how it relates to the clarity and focus on an image captured by a digital video camera. The lens in camera contorts light, and this is directly decided by the focal length. When you are setting up a focal length in your camera you zoom in to a long distance on a specific object. This object can then be known as your focal plane. Every object from that object back to the lens will then remain in focus.

This is often referred to as focusing in infinity, or some verbal variation similar to that phrase. The space between what has now been established as the focal plane and the lens that will bend and interpret the light that comes in is the relative focal length. This focal length includes all of the spaces that are hence forth in focus after the original calibration of zoom to infinity.

The distance of a focal length is often determined by the lens you are using in your digital video camera. Fixed focal length lenses have a single focal length, often like the ones found in some old film cameras. The more common zoom lenses have many different focal lengths.

When setting up a focal length with your camera you really have to determine the proper framing for your particular purpose. You decide the position of the focus object and how large they should be. Then calibrate focus on them, determining the focal length. In this way the focal length is relative to the size of the image of the object, and both are connected to the positioning of the camera in relation to the object and the size of the lens.

Remember that the position of the camera is going to have similar effect to the zoom in relation to the focal length, even though there are definite changes in over all image perspective between the two movement approaches. Though zoom does determines focal length, the space between the object and the camera has an effect as well.