Depth of Field Calculator

This depth of field calculator, or DoF calculator, will help you take more fantastic portrait and landscape shots by understanding your camera better when it comes to the depth of field. Take your depth of field photography to the next level with a solid understanding of:

• What depth of field is;
• What circle of confusion is;
• How to adjust the depth of field;
• The different depth of field formulas; and
• How to calculate the depth of field.

Depth of field is the distance between two planes, a closer one and a farther one, in which we can position objects to have an "acceptably sharp" image formed in a camera. Objects beyond the depth of field will appear blurred or out of focus. On a manual camera, we can set a wide or deep depth of field to capture more details of a scene, or we can have a narrow or shallow depth of field to focus on a particular object while blurring out the background or the foreground as shown in the image comparison below:

We can achieve these depths of field by changing:

• Our camera's aperture area;
• The lens we use to explore different focal lengths; and
• Our distance to our subject or our focusing distance.

But first, how come we see blurred areas in the images we capture? We can explain that using the concept of the circle of confusion.

Imagine an arbitrary point where we focus our camera. As light bounces off this point and travels towards our camera's aperture opening, it spreads out and starts to get blurry. The more it spreads out, the blurrier it gets. The maximum size spot of a circle this point can spread out before we consider it out of focus is called the circle of confusion.

The diameter of the circle of confusion, which we also call the circle of confusion limit, defines how deep the depth of field is. We can observe the circle of confusion in two instances: one between the camera and the focusing distance and one beyond the focusing distance. We call the distance from the camera toward the first circle of confusion the depth of field near limit, while the distance from the camera towards the second circle of confusion is the depth of field far limit, as shown in this illustration:

The circle of confusion limit depends on various factors such as the camera's sensor size, the viewer's visual acuity, and the enlargement of the image produced by the camera to print size. We'll learn more about this in the following sections of this text.

Aperture area

Using a small aperture opening, we can achieve a deep depth of field where we can capture an acceptably sharp image of near and far objects, as illustrated below:

Focusing distance

When taking pictures, we almost always want our subject to be within these two limits or the depth of field. We may also choose to keep our subject's foreground and background in focus or not.

From our previous example, if we shorten the focusing distance while maintaining the same aperture size, we decrease the depth of field, as shown below:

We still have a deep depth of field; however, the kitchen countertop now lies beyond the depth of field and, therefore, out of focus. Now, let us increase the size of our aperture. Doing so allows light to spread wider, which results in a shorter distance to reach the circle of confusion limit, giving us a narrow depth of field, as we can see in the image below:

With the same large aperture opening, we can also change our camera's focusing distance towards our foreground object (in this case, the electric fan) and make the rest of the scene blurry, as shown in the image below:

By having a short focusing distance towards our subject and using a large aperture opening, we can see that the light spreads faster, resulting in a very narrow depth of field. The same thing happens when we take macro or close-up photos.

Focal length

As a rule of thumb, we use longer lenses when we want to take shallow depths of field shots. On the other hand, wide-angle lenses and lenses with short focal lengths are great for deep depth of field photography.

In the next section of this text, we'll discuss how to use this DoF calculator. Then, we'll dive deeper into calculating the depth of field manually.

Here are the steps you can follow when using our DoF calculator:

1. Select your camera's sensor size from the list. You can enter custom sensor width and height measurements by selecting Custom sensor size from the options.
2. Enter the focal length of the lens you are using.
3. Pick the aperture size you prefer to use.
4. Enter your approximate focusing distance to your subject.

Upon doing these steps, you'll get the depth of field and depth of field limits for your camera's settings. If you think the calculated depth of field is either too narrow or too wide for your liking, you can adjust your camera settings to meet your preference.

Our DoF calculator uses a default value of 0.029 mm for the circle of confusion limit of a 35mm full-frame sensor size. You can check the Show advanced details checkbox under the Focusing distance (u) variable of our calculator to change this value or modify the values of the factors that affect the circle of confusion limit.

Upon showing the advanced details, our DoF calculator will also display the corresponding focal ratio of your selected aperture f-stop, the approximate hyperfocal distance, and the hyperfocal near limit of your entered settings. We'll get more into these parameters in the next section of this text. And if you want to explore even further, feel free to visit the hyperfocal distance calculator.

We have two depth of field calculation formulas that we can use. In the previous section of this text, we mentioned that the depth of field is the distance between the depth of field far limit and the depth of field near limit. We can express that in an equation form like this:

That would be easy if we can right away physically measure the depth of field far and near limits. However, if we cannot measure them, we can calculate them using these formulas:

• $DoF_{\text{far limit}} = \frac{H\ \times\ u}{H\ -\ (u\ -\ f)}$

• $DoF_{\text{near limit}} = \frac{H\ \times\ u}{H\ +\ (u\ -\ f)}$

where:

• $H$ — Hyperfocal distance;
• $u$ — Focusing distance or the camera's distance to the subject;
• $f$ — Focal length of lens used.

Hyperfocal distance is the focusing distance in which we get the maximum depth of field, and we can calculate its value using this equation:

where:

• $f$ — Focal length of lens used;
• $N$ — Aperture f-number; and
• $C$ — Circle of confusion limit.

The circle of confusion limit, which we know determines the depth of field, depends on several factors, as shown in the equation below:

where:

• $d_{\text{av}}$ — Actual viewing distance of a printed photo version of an image; and
• $d_{\text{sv}}$ — Standard viewing distance that a person can observe the said printed photo through a defined visual acuity;
• $\text{visual\ acuity}$ — Resolution at which a typical viewer can distinguish details in the printed photo at the standard viewing distance in terms of line pairs per mm (lp/mm); and
• $\text{enlargement}$ — Enlargement factor of the image produced on the film or camera sensor into the printed image.

Enlargement factor is essentially the ratio of the diagonal of the printed image ($\small{\text{diagonal}\_\text{p}}$) and the diagonal of the camera's sensor ($\small{\text{diagonal}\_\text{s}}$). Expressed in equation form:

To calculate these diagonals, we can use the Pythagorean theorem, as shown in the equations below:

• $\text{diagonal}\_{\text{p}} = \sqrt{w_{\text{p}}^2 + h_{\text{p}}^2}$

• $\text{diagonal}\_{\text{s}} = \sqrt{w_{\text{s}}^2 + h_{\text{s}}^2}$

where:

• $w_{\text{p}}$ — Width of print;
• $h_{\text{p}}$ — Height of print;
• $w_{\text{s}}$ — Width of sensor; and
• $h_{\text{s}}$ — Height of sensor.

Alternatively, we can also use this simplified depth of field calculation formula:

where:

• $u$ — Focusing distance or the camera's distance to the subject;
• $N$ — Aperture f-number;
• $C$ — Circle of confusion limit; and
• $f$ — Focal length of lens used.

Understanding depth of field can help you take great pictures, whether of people, still objects, or landscapes. But remember that as we change our camera's settings, especially the aperture size, we may also need to adjust our camera's exposure and shutter speed settings. You can check our exposure calculator and our shutter speed calculator to learn more about these other settings. 📸