Circle of confusion in Virtual Production

Circle of Confusion is a Cinematography term in filmmaking. In virtual production, the nuances of this term take on special meaning. Here, we break down the definition to give you a starting point.

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Basic Definition:

What is Circle of confusion in virtual production?

The measurement of where an unfocused point of light becomes a circle passing through a lens onto the film back or digital sensor of a camera. Is a characteristic of the lens’s depth of field. See also Bokeh.

The purpose of Circle of Confusion (COC) is to indicate how much blurriness should be expected from different focal lengths, thus allowing cinematographers to more accurately focus on specific objects while blurring out background elements. The smaller the COC value is, the better defined the edges are around your subject, leading to a sharper image. A larger COC value will create a softer feel and greater depth-of-field. 

When shooting with a digital camera, you can control the size of the circle of confusion by adjusting aperture settings which controls how wide open the iris blades are and allows more light into the lens; hence changing the COC. Additionally, focusing techniques such as rack focusing also aid in manipulating the amount of blurriness within a frame.

In Virtual Production, the use of a Circle of Confusion is incredibly beneficial because it helps establish visual consistency between foreground and background elements, making green screen compositing easier and providing better results. Furthermore, by controlling the size of COCs, DP’s have better control over what parts of the scene they want to keep sharp while still keeping some movement in the background.