Circle of Confusion in Photography appears as light is actually a cone of photons, it is not designed by nature to be captured on a flat surface. Circle of Confusion is quite difficult topic under optics and in this article only the basics of Circle of Confusion in Photography will be discussed.
What is Circle of Confusion in Photography ?
As I have said – in nature everything gets designed to accept and be compatible with each other, like there is little Circle of Confusion arises in case of human eyes under normal condition as the retina is concave and processing of image in human is done by “dedicated department”, it is not only simple optics, but many less understood, not yet discovered things plays a big role there to negotiate Circle of Confusion. Human eye is a prime lens but the focal length can be changed.
Circles of confusion arises in the photograph at blurring of the image, when the projection of a point of a subject before or behind the projection plane or by diffraction to a point of focus is mapped. Special significance of the circle of confusion is in the calculation of depth of field.
As we all know, the light is becoming like a cone and we are chopping the cone with a plane – be it film or sensor. Not all cones are actually becoming a point when it is actually reaching the plane. This is the easiest way to understand Circle of Confusion. In case of human eye, Circle of Confusion is very less as the retina is designed by the great craftsman in an way that almost 98% area is free from Circle of Confusion.
In case of photography circle of confusion diameter is taken where the largest blurred spot can be perceived by human eyes as a point. This is used for Circle of Confusion in practical purpose as your eye in real, never face such blurred spots – they are trimmed out while processing by your brain.
Need to know this Circle of Confusion in Photography
Now you have understood what is Circle of Confusion. We basically need a bit Circle of Confusion in Photography to make a realistic pseudo depth. There is a thing that is known as Maximum tolerable diameter for circle of confusion. Maximum tolerable circle of confusion diameter for a camera is denoted by Z. There are many mathematical formula are used for adjusting this Circle of Confusion and size of Sensor or film. Otherwise without knowing the Circle of Confusion, other parameters can not be standardized.