The circle of confusion is a term in photography used to determine how much detail a lens can resolve. The circle of confusion refers to the size of the area around an image’s focus point that appears to be equally in focus.

This must be calculated for a specific sensor format and lens combination, but the effects are universal.

If you use lenses below their maximum resolving power, you’ll begin to see pixelation (noise) and artifacts in your images.

Anything that falls into your frame that exceeds the circle of confusion will appear out of focus in your photo.

circle of confusion In photography

What Is The circle of confusion In photography?

The circle of confusion (CoC) is an expression that appears in lens design. It defines the maximum size a point source of light can have, before it is perceived as a blur spot by the human eye.

The circle of confusion diameter is used to define the depth-of-field near limit, far limit and hyperfocal distance.

It is theoretically possible that two objects at different distances from the camera will project an image on the same plane.

In reality, due to imperfections in lens design and construction, a slight difference in distance produces a different image position on film. This fact becomes important when we discuss depth of field.

The circle of confusion is a subjective value. A larger CoC makes for more depth-of-field and creates less critical focusing requirements. A smaller CoC means less depth-of-field and more precise focusing requirements.




To understand how it works, you must first know how cameras can focus on a target. There are two types of focus; autofocus and manual focus.

Autofocus uses an internal light meter to determine what it thinks is the right focal point, then it adjusts the lens until it reaches that point.

As you can imagine, this can get very confusing, especially when there are several objects close together that have different focal points.

Manual focus allows you to set the focal plane yourself by looking through the lens and moving the focusing ring until it reaches the right point.

Once you have determined what part of your picture you want in focus, you then need to decide how much depth of field you want in your shot.

This will be determined by how large the circle of confusion will be when taking your photo. The larger the circle of confusion, the more things will be in focus.

What Is The Circle Of Confusion In Photography?

The larger the sensor format, the smaller the CoC needs to be since it encompasses less of the image sensor.

The standard way to express the CoC is by giving it a diameter in millimeters. It is also expressed as a fraction or multiple of the focal length — this is because different lenses have different resolving power at different focal lengths.

For example, if you are using a 35mm lens on a full-frame camera, then you need about 0.03mm CoC for everything to be in focus. If you are using a 100mm macro lens, then you need about 0.3mm CoC for everything to be in focus.

Circle Of Confusion Diameter Limit In Photography

I’m often asked what is the circle of confusion (CoC) diameter limit in photography. I’ve been getting a lot of questions lately, so I thought it was time to re-post this information.

The Circle Of Confusion (CoC) is the diameter of the blur spot that appears when an image is out of focus. The CoC is also described as the depth of field. A large CoC means that an image appears out of focus and can result from a wide aperture and/or large sensor size or focal length. For example, a full-frame 35mm camera with a 35mm lens focused at approximately 1 m will have a CoC of 0.35 mm at f/1.4 while a 1 cm CoC diameter would be expected at f/22.

So, what is the CoC limit? As far as I know, there isn’t one set number but rather it varies with each camera model and lens combination. It’s generally very small for compact cameras and lenses designed for digital cameras but gets larger for DSLRs and lenses designed for film cameras.

The table below shows approximate values for various cameras based on my test results with typical lenses used on each camera body: Camera Type Approximate Circle Of Confusion Diameter (mm).

What Is The Circle Of Confusion

A circle of confusion also called the critical circle diameter (CCD), is a term used to describe how much blur can be seen in an image. This is important when you are taking pictures because it determines the depth of the field.

The circle of confusion (CoC) is used to determine the acceptable limits of sharpness in an image. Any area in an image that is not considered to be sharp enough could be considered an unacceptable area and could be edited out. The larger the CoC, the larger the blur radius is, which determines how many objects that are out of focus can remain in an image before it is no longer acceptable.

The size of the circle of confusion (CoC) depends on several factors:

Lens focal length and aperture setting. The smaller the aperture setting and longer the lens focal length, the larger the circle of confusion becomes.

Image sensor pixel size. This is directly related to pixel size; forgiven pixel size, as you increase the focal length or decrease the f-number, you increase CoC.

Image format and resolution. This depends on how many pixels there are per inch; at higher resolutions, CoC decreases in size.

Importance Of Circle Of Confusion In Photography

The Circle of Confusion (CoC) is a vital element in photography. This explains why the subject detail in a photograph is often blurred. In this article, we will define the CoC and discuss the factors affecting it, as well as its applications.

Let’s start with an explanation of what is a circle of confusion. In essence, it is a “blur” to which an image can be compared to find out what is or is not in focus. It is particularly relevant in photography as it helps you evaluate the sharpness or otherwise of your image at any given point.

What is the Circle of Confusion (CoC)?

The CoC represents the smallest object that appears to be perfectly sharp when viewed from a certain distance. In other words, if an object measured smaller than the CoC cannot be perceived as sharp by your eyes, then it cannot appear sharp when captured by your camera either – because there will be no difference between how your eye sees the subject and how the camera sees it. For example, if you were taking a picture of a flower with a macro lens and you were shooting from 10cm away, then the CoC would be 10mm (or 0.1cm).

Circle Of Confusion Diameter Limit Based On D/1500

Now that you know how to calculate the circle of confusion diameter limit based on the film format, you probably want to know what it all means. Let me explain.

When we photograph an object and make a print, the image of that object is reproduced as a two-dimensional image on a sheet of paper or film. (You can read about this in more detail here:

The dots of color that make up this image represent tiny areas in the original object; these areas are known as pixels or picture elements. The size of the pixel is determined by the size of the CCD used to capture the image and by the magnification of the final print. The greater the magnification, the smaller the pixel, and therefore, the sharper it will appear in your final print.

The circle of confusion is an optical measurement that determines how “sharp”, or how much detail, can be captured on film or paper. As described above, for any given circle of confusion diameter limit, there will be a range of distances from which objects will appear acceptably sharp when viewed in a final print.

Adjusting The Circle Of Confusion Diameter For A Lens’s DOF Scale

I decided to write this article after I received several emails from people looking for answers to the same question:


“How do I calculate the CoC (circle of confusion diameter) for my lens? The tables in your articles are not right for me.”

Since I wasn’t answering this question properly, I decided to make a new table, and provide an explanation to go along with it.

The first thing you should know is that there are two ways to calculate the circle of confusion diameter. One is the “old way” (for lack of a better term) and one is more modern. These calculations are different enough that they give different results even when the same information is used. So, what’s the difference?

When you’re using the “old way”, you are calculating the minimum size spot that will be recorded as a point in your image.

While this can be used as a measure of “blur” caused by things like subject movement or camera shake, it can also be misleading if you don’t understand what you’re looking at. Why? Because other factors can cause blur (or “noise”) in your images, such as:

Determining A Circle Of Confusion Diameter From The Object Field

The Circle of Confusion defines the limit of sharp focus in a photograph. When you set the f/stop on your lens, you are determining how large a circle of confusion can be created. The larger the circle of confusion, the more detail that is lost.

To calculate the Circle of Confusion diameter, we will use the Focal Length and F-Stop. Since we know that for a given f-stop number (f/8 for example), the circle of confusion diameter increases as the focal length increases, we can set up a formula based on this information:

COC = 2 * f * tan(A)

COC = Circle Of Confusion Diameter

f = Focal Length

A = Angle of view in degrees (This can be calculated with our Field of View calculator)

This formula works well for all focal lengths with apertures from f/4 to f/22, but it is not very accurate with wider apertures than this due to diffraction. It also works only for a full-frame 35mm camera or lenses with a full-frame 35mm equivalent focal length.

Effects Of The Circle Of Confusion In Photography

The circle of confusion is a key concept in photography. It refers to the point at which an image becomes indistinguishable from a blur. As we will see, the size of this blur increases as the aperture decreases.

To understand the concept of a circle of confusion, let’s consider how our eyes and cameras work. We begin with some basic definitions:

–       Resolution: This is the amount of detail that can be discerned by the eye or camera. The higher the resolution, the better we can see fine details in an image or scene.

–   Field of View (FOV): This is how much an object appears to be magnified when we look at it through a lens or viewfinder. The higher the FOV (i.e., the wider the lens), the more you can fit into your frame.

When you look at an object with your eyes, you get a wide field of view and high resolution. You can see small details in objects that are close to you, such as text on a page or brush strokes on a painting.

However, when you move farther away from that object, your field of view narrows and so does your resolution. When you get so far away that you cannot distinguish individual brush strokes, it becomes a blur to your eyes.

Hyperfocal Distance, Depth Of Field, And The Circle Of Confusion

If you’re using a standard focal length lens, and your hyperfocal distance is 50ft then everything from 25ft to infinity will be acceptably sharp.

This was tested by the US military in the 1940s as a way of ensuring that all soldiers had their rifles sighted incorrectly. The procedure was simply to fire at a target 25m away and then measure how far out the bullet holes and splashes of mud extended from the point of impact. This distance should then be marked on the sight for that weapon.

This method works for other distances too and is perfectly acceptable, but it does rely on having an accurate rifle with perfect sights set to exactly the right distance, which can be difficult to achieve.

A better method that still relies on the same principle is to set up sight as if you were going to fire at infinity, but then look through the rear aperture and see where the target appears to be about some fixed point (e.g., a marker pen on the gun).

Then simply adjust your sight until this point appears exactly between your front and rear sights when looking through the rear aperture.

Bokeh And The Circle Of Confusion In Photography

We are often asked about the Bokeh effect. What is bokeh? How do I achieve it? In this article, I will attempt to explain what the circle of confusion is and how it relates to the Bokeh effect in photography.

TTL stands for Through The Lens. TTL metering is done by a secondary method, usually a separate meter reading off the film plane through the lens. This method works well because it doesn’t need to worry about light bulbs burning out or filters being changed on your lens.

There are two types of TTL readings: Matrix Metering, and Center-Weighted Metering.

Matrix Metering can be regarded as a full-frame reading while Center-Weighted Metering gives more weight to the center portion of the frame. By default, most modern DSLRs use Matrix metering with some providing an option to switch to Center-Weighted metering. Your camera manual should tell you if your DSLR allows you to change between these two modes.

Matrix meters take into account everything in your scene and then give priority to what it thinks is most important (usually people). This can cause problems when photographing a subject against a busy background where the camera might think that the subject is less important than the background.

Final Words About The Circle Of Confusion

The circle of confusion (CoC) represents the region on an imaging sensor where an optical system forms a focused image. It is mathematically calculated by dividing the diameter of the entrance pupil of the lens by the pixel pitch (in micrometers).

The CoC defines the resolving power of an image sensor and its ability to capture fine details. This number is rarely published by camera manufacturers, but it affects how we perceive images, so it’s important to understand what it is and how it works.

Other factors that affect how sharp an image looks are related to diffraction: lens aberrations, optical imperfections, atmospheric conditions, and more. A 135mm f/2.8 medium-format lens at f/2.8 will produce fewer sharp images than a 24mm f/1.4 full-frame lens at f/1.4 in ideal circumstances because it has a larger CoC (0.68 vs 0.28), where each pixel covers more of the image area.

The bottom line: if you want to know how good a given camera is at producing detail, you have to know its pixel pitch and circle of confusion first before making any assumptions from other specifications like resolution or apparent focal length.