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circle of confusion in photography

Explained: Circle of Confusion and its Impact on Photography

Explained: Circle of Confusion and its Impact on Photography

In this article I will explain what is Circle of Confusion in Photography, this might sounds strange to the art oriented students, if you have studied physics you will be familiar with the term ‘Circle of Confusion’  It is one of the less explained aspect even at high school, as a lover of photography you should endeavor to learn by reading through as I will guide you through since it is a very important concepts in photography. If you want to take photo professionally you need to learn how to deliver sharp and clear images(pictures).

What is Circle of Confusion in Photography

Apart from the most talked about factors in photography (aperture, focal length and distance) there is another that also affect the sharpness of an image,  it is called ‘circle of confusion’. It’s a technical concept, but I’ll try to make it as simple as possible in order for you to understand.
Basically, I was so bored the first time I read about it and I don’t want to do this to you. Let’s delve into it.

Do you know, understanding the circle of confusion will take you closer to the goal of taking wonderful images.

Explained: Circle of Confusion and its Impact on Photography
Understanding how camera lenses work and how they are able to focus light makes it easier to appreciate how the circle of confusion works.

Before I proceed, I’m going to simplify this concepts for this article. I know a lot of people have once asked What is Circle of Confusion in Photography, if you’re an expert or know how these things work already, bear with me and don’t hesitate to write in the comments section below if something I say could be explained better, since we are all in the learning world.

When the focus point and the focal plane do not meet, a point source of light (a round light source) appears slightly bigger and no longer appears to be in sharp focus. However, there is a certain range of tolerance in front of and behind a subject before it starts to appear out of focus to the human eye; that range is what is known as circle of confusion. In the below representative diagram the range is highlighted by the purple rectangle.

DO YOU KNOW? How Camera Lenses Work
In a convex lens, parallel rays of light are bent inward thanks to a phenomenon called refraction. See image below.

Light rays that travel through the lens are refracted and converge to a single point. That point is called focal point.

circle of confusion in photography

Producing a Sharp Image
Let’s try to understand how your camera focuses light.

The process I’ve explained above is not enough by itself to produce a sharp image. One single lens is not enough.

Explained: Circle of Confusion and its Impact on Photography
As one single convex lens by itself is not able to produce an in focus image, camera lenses have multiple lens elements inside to help with this process. Without going too much into detail this is the reason why certain lenses are more expensive than others. They might have more lens elements inside to produce better quality images, avoiding imperfections such as chromatic aberration.

circle of confusion in photography

Back to sharpness. For a subject to be perceived as in focus by our eyes, points of this object have to be projected by the lens onto the sensor (also known as focal plane) in a way that the focal point is aligned with the focal plane. See image below.

Circle of Confusion and its Impact on Photography

The image is overly simplified. The focal plane never moves, in reality the focus element (not represented) of a lens moves back and forth until light is refracted so that it aligns with the focal plane. The image will be unsharp when the point is off the focal plane and vice versa it will be in focus when it’s aligned.

circle of confusion in photography

If all this make sense to you we are very close to define the Circle of Confusion. There is a certain area in which despite the point being outside the focal plane, it’s still perceived as sharp by our eyes. That is the Circle of Confusion and the image below explains it much better.

Circle of Confusion and Depth of Field
We know that to get the sharpest possible images we need to be bale to get the depth of field right. The depth of field depends from they Hyperfocal Distance which is the focusing distance that gives you the greatest depth of field.

So why is the circle of confusion related to depth of field?

It’s because the measurement of the circle of confusion is used by camera manufacturers to determine the Hyperfocal distance of a lens.

Read More: How to Clean Your Camera Lenses and Filters by Yourself

If you want to know more about the following: circles of confusion vs bokeh, Circle of Confusion and its Impact on Photography, circle of confusion pixel size, circle of confusion production movies, circle of confusion physics, depth of field photography, fuji xt2 circle of confusion, hyperfocal distance, panasonic gh5 circle of confusion, endeavor to bookmark our  page.

What is in or out the circle of confusion is what we define in or out of focus. I hope that my simplification of this complex concept helped you understand it a bit more.

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