The Circle of Confusion Impact on Photograph

Circle of confusion (CoC) is defined as the degree of tolerance that the human eye has before it differentiate between an object that is out-of-focus and one that is in focus. In photography, this technical term used quite often and it is also known as blur circle, blur spot, the disk of confusion or circle of indistinctness. It helps in the measurement of a point of light.

The circle of confusion is related to how your lens focuses and aperture value. A small aperture will change the convergence. Different focal length results in different Circle of Confusion. It affects the depth of field. It also influences how some lenses to produce softer images. Point of light cannot be resolved by a lens. So, it creates a tiny circle refers to as Circle of Confusion.

Light travels from a point source (round shape) appear slightly bigger and no longer in sharp focus when the focus point does not line up with the focal plane. The lens contains many elements through which light travel and then strike on the sensor inside the camera. Here are many elements in the lens but the important one is the focused element.

This focus element refracts the light toward focus point. You have good focus, If focus point meets up with the focal plane. When the adjustment of focus is done then focus element moves the focus point. There is a direct relationship between the sharpness of the lens and the Circle of Confusion. The measurement of Circle of Confusion in fractions of a millimeter.

Three Factors that determine the Circle of Confusion are:


Here original refers to the image on our actual sensor. Your final image is 24mm by 36mm and any final production of your image beyond that is technically considered an enlargement.


Distance is another factor that determines the Circle of Confusion (CoC) by viewing your final image from the distance.  If the distance between you and the image is less than you are more likely to perceive a blur spot as blur spot and not as a single point.

Visual acuity

In simple words, it is the clarity of vision or sharpness of vision. We have no real control over it but have some idea about what is normal.

I hope you like this interesting topic and it will help you to enhance the overall quality of your final images.  Here, some information about the circle of confusion provided by Haythem Lafhaj and see what difference this new found knowledge will make to your photography.

Also read: Depth of field as an important tool in photography

Preetika Sharma