Circle of Confusion (CoC) Calculator

How to use the Circle of Confusion (CoC) Calculator

I know that Circle of Confusion (CoC) is a concept that is difficult to understand because it's hard to visualize in your mind. It’s something that you cannot touch with your hands nor see with your own eyes. I must confess that it freaked me out at the beginning!

But, there is no reason to be scared. The Circle of Confusion is just a number that represents the diameter or the maximum size that a blur spot, on the image captured by the camera sensor, will be seen as a point in the final image by a viewer for a given viewing conditions (print size, viewing distance and viewer’s visual acuity).

As a result, once you’ve decided the values of sensor size, max. print size, viewing distance and visual acuity, you can calculate the Circle of Confusion. By doing so, you’re establishing the convention of what is considered to be acceptably sharp in the image.

In other words, you’re defining when a blur spot on the camera sensor will be seen unsharp on the final image. You’re building the frontier between sharpness and unsharpness. And this frontier, the Circle of Confusion, will allow you to calculate the depth of field values.

On the one hand, this Circle of Confusion calculator will help you understand how sensor size, max. print dimension, viewing distance and visual acuity influence the CoC. And, on the other hand, it’ll make all the calculations for you.

Just introduce the following settings in the calculator to get the Circle of Confusion.

  • Camera model (camera sensor size): Any blur spot you see in the final image is an enlargement of a blur spot captured by the sensor of the camera. Thus, sensor size is used to calculate the enlargement of a blur spot given by its proportion with image print size.
  • Maximum print dimension: The size you want to print the photo.
  • Viewing distance: The distance between the viewer and the printed photo.
  • Visual acuity: Defines the quality of the viewer’s vision.

Most depth of field calculators assume that for a given sensor size, the Circle of Confusion is calculated using a print size of 8''×10'' (20cm×25cm), a viewing distance of 10" (25cm) and the manufacturers standard visual acuity (the viewer can perceive details which size is roughly 0.01”).

But, if you want to get more control over what is seen in focus or blur in your final print images. Let's say that you want to change the viewing conditions. Then, just set the new viewing parameters and calculate the adjusted Circle of Confusion. Finally, plug the CoC in PhotoPills’ Advanced DoF Calculator to get the adjusted depth of field values.

Using an adjusted Circle of Confusion for your depth of field calculators is extremely useful when you want to print one of your photos in a larger format (for example, 2.29x4.92ft - 70x150cm).

The typical example is when you want to print a beautiful landscape in large format. Before the shooting, you need to calculate the adjusted CoC considering the new hypothesis. By plugging this CoC within PhotoPills' Advanced DoF Calculator, you'll get the hyperfocal distance.

This adjusted hyperfocal distance is the distance at which you need to focus the lens to maximize depth of field in the printed photo. 

Understanding Circle of Confusion and Depth of Field

If you’re interested in learning more about Circle of Confusion and depth of field, take a look at the following article:

The Ultimage Guide to Depth of Field (DoF)

You’ll learn everything you need to shoot stunning deep depth of field images...

... and also to shoot storytelling shallow depth of field photos.

The Circle of Confusion (CoC) Calculator in PhotoPills app

The CoC calculator is also available in PhotoPills app. You'll be able to personalize the Circle of Confusion using the Advanced mode of PhotoPills' Depth of Field Calculator. 


PhotoPills' Advanced DoF Calculator.

PhotoPills' Advanced DoF Calculator - CoC Calculator.

Finally, If you're interested in learning how to imagine, plan and shoot the sun, the moon and the Milky Way, take a look at the following How-to articles:

How to embed the Circle of Confusion (CoC) Calculator on your website

Take the power of PhotoPills’ CoC Calculator with you. Just copy the following lines and paste them within the code of your website, right in the place where you want to embed it:

<div id="ppcoc"></div>
<script src="//photopills.com/widgets/ppcoc.min.js" async></script>

The code will run asynchronously, without penalizing the loading time of your website.

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