Learning the lingo around depth of field
Depth of field
A measure of how much of a picture is in focus, from the nearest point in the scene to the camera that looks sharp, to the furthermost point that looks sharp.
Depth of Field Preview
A feature on some cameras that enables you to see the viewfinder image at the actual aperture you’ll be using for the exposure. This will give you a visual indication of how much depth of field there is.
Circle of confusion
A point on a subject only appears as a point on the image if it’s perfectly in focus. If it is not, the point appears as a circle in the picture. The more blurred the picture, the bigger the circle.
If the circles are small enough, however, that part of the picture will still look sharp. The largest-sized disk that looks like a point is known as the ‘least circle of confusion’; this scientific measurement is fundamental to accurate calculation of depth of field.
Optical term to describe objects so far away that light from them reaches the lens as parallel rays. It is generally used to describe objects that are on or near the horizon.