# Circles of Confusion

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### #1 Steve London

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Posted 13 July 2009 - 03:29 AM

It's a night exterior, the camera is focused on a couple five feet away, shallow DOF, and in the background, the hundreds of Christmas lights down the street make attractive little out of focus circles of colored light. They are circles of confusion, correct?
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Posted 13 July 2009 - 08:03 AM

No. Circle of confusion has to do with depth of field calculations, e.g what distances an object will be out of focus on a specific lens at a specific f-stop.

http://en.wikipedia....le_of_confusion
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### #3 K Borowski

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Posted 13 July 2009 - 09:25 AM

Well, they illustrate the circle of confusion, though, Adrian.

If, say, the circle of confusion is 1/1000 of an inch (~25 micrometers), that will be the size of a point of light in focus.

When something is out of focus, its circle of confusion increases, making it softer, fuzzier.

So, Steve, out of focus lights have a larger circle of confusion, and, hence are more fuzzy, as the light isn't focused into a smaller, tighter point.

The circle of confusion concept comes into play because, there is no such thing, really, as being perfectly in focus, only resolving to a point of a certain size.

Obviously, the smaller the point, the more focused the light will be though.

Depth of field comes into play when you are calculating for points of confusion of a certain size (think they are measured in diameter size?)

Forget, off the top of my head what the equation is for out of focus or soft focus circles of confusion if you wanted to make out of focus Christmas lights a certain size; again, obviously the more out of focus the larger they'll be. But, I am sure the equation for COC size is on Wikipedia too.

Edited by Karl Borowski, 13 July 2009 - 09:26 AM.

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### #4 Tom Jensen

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Posted 13 July 2009 - 12:27 PM

I always thought it was when the producer, the director and the AD huddled together. That's what I called it.
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Posted 13 July 2009 - 12:32 PM

ba drump cha (my drum sound)
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### #6 Chris Keth

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Posted 14 July 2009 - 12:02 AM

Forget, off the top of my head what the equation is for out of focus or soft focus circles of confusion if you wanted to make out of focus Christmas lights a certain size; again, obviously the more out of focus the larger they'll be. But, I am sure the equation for COC size is on Wikipedia too.

The equation for getting out of focus points the size you want is 1. shoot more wide open or 2. yell to the art dept people to walk those christmas lights further down the street.
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