Depth of field : Everything you need to know

In this article I will fascinate about what it is and how to use Depth of Field. We will talk not only on the surface of the subject, but we will also go deeper so that you can bury how to use this tool so important in photography.

What is depth of field?

Depth of field refers to the distance range in which a photo appears with acceptable sharpness.

This varies depending on the type of camera, apertures and distance, although print size and viewing distance can also influence our perception of depth of field.

This tutorial is designed to provide a better intuitive and technical understanding for photography.

Depth of field does not abruptly change the sharpness of the photo, but instead a gradual transition occurs.

In fact, everything immediately in front of or behind the focus plane is already starting to lose sharpness – even if it’s not noticed by our eyes or the camera sensor.

Since there is no critical point of transition between blurring and focusing a more rigorous term called the ‘circle of confusion’ is used to define how blurry a point needs to be in order to be seen as blurred.

When the circle of confusion becomes noticeable to our eyes we can say that the region is outside the depth of field and at this moment no longer “acceptably clear”.

How to control depth of field

While print size and viewing distance influence how large the circle of confusion appears in our eyes, aperture and focus distance, or focal length, are the two main factors that determine how large the circle of confusion will be on the camera sensor.

Larger apertures (smaller f-numbers) and closer focal lengths produce a lower depth of field. The following test maintains the same focus distance, but changes the aperture setting:

Example of using depth of field
Example with aperture F/3.5. Shutter at 1/50 s and ISO 100
Example of using depth of field 2
Example with aperture F/3.5. Shutter at 1/50 s and ISO 100
Example of using depth of field 3
Exampl with aperture F/5.6. Shutter at 1/20s and ISO 100
Example of using depth of field 4
Example of depth of field with F/8 aperture. Shutter at 1/10s and ISO 100
Example of using depth of field 5
Example with F/11 aperture. Shutter at 1/5s and ISO 100
Example of using depth of field 6
Example with F/16 aperture. Shutter at 1/2s and ISO 100

In the photos above you can see how the aperture can handle the DOF.

Notice that when I close the opening the bottom brushes are getting sharper, in fact I’m increasing the depth of field in a way.

Photos of the brushes taken with a Nikon D5200 and a Nikkor 50mm f1.8G lens.

Isn’t depth of field the same thing as blurring from the bottom?

This is the most common misunderstanding among novice photographers, a vague confusion between DOF, Depth of field or depth of field and background blur.

Now, it is true that DOF is a tool that we use, and a lot, to selectively blur parts of an image, to isolate the bridge of interest or even to create what we call selective focus.

But to think of DOF as just a way to blur the background is to kind of lose a little sense of things.

Why in fact the sense of depth of field is going exactly in the opposite direction of blur. After all the term depth of field does not refer to the parts that are blurred in the image. It’s about the acceptable focus distance.

Here’s a definition of work I like.

Depth of field (noun): The distance range in an image where the focus is acceptably sharp.

Here’s an example where background blur is used as a tool to isolate the object of interest in the image:

Statue

Bronze Panther by Rix Mascarenhas on 500px

How to use depth of field – Tip 1

If you want to blur the background as the object away from it. It is much easier to blur a background than this 9 meters behind its subject to be photographed than one that is 60 centimeters than will be photographed.

The closer you are to your object being photographed the easier it is to blur the background. Think of it as a reason: the distance between you and your point of interest versus the distance between the subject and the background.

Woman's face
Lens 100mm F/4 at 9 meters

How to use dOF – Tip 2

It is possible to exaggerate with a shallow depth of field. You can make the depth of field so small that you lose parts of the face of the person who is photographing himself, in the case of portraitists.

Broad face
Note how part of her hair and right eye begin to become blurry.

Use depth of field to create foreground blur

Foreground blur is often overlooked by photographers when they think about DOF, probably because each photo has a background, and almost always they are arranged to have nothing in the foreground other than the main object.

The classic example is to blur the background in a portrait to draw attention to the face in the case of portraits. However, having blurred objects in the foreground can give a sense of framing, depth, or context to a photo.

Or even to make such a selective focus, where it isolates the object of interest even if for this it has to blur the foreground

Blur foreground
Foreground blur

You can also use foreground blur to remove obstacles that are between you and the object to be photographed.

The next photo was taken from the stands, between the car that was photographed and the photographer existed the grid. This grid can barely be seen due to foreground blur.

Racing cars
Foreground blur by removing objects

What is Bokeh?

Photographers in general usually often use such a term. Often referring to certain lenses such as those that give “good bokeh” or “bad bokeh” to determine the quality of the lens.

Well anyway everyone is behind a lens that can blur the background with what we call circular bokeh.

Bokeh

Some lenses have better ability of such an effect in the foreground, others in the background and anyway there is no relationship.

So if you want, and at some point you want to, experiment with your lenses and see what kind of bokeh they give you the foreground blur and or background blur.

The easiest way to see the shape of bokeh is to take a picture with small lights in the background or foreground that are out of focus, so you’ll know what kind of blur you have.

Conclusions

DOF manipulation is a good way to modify the characteristics of your photo, and manipulating the aperture is the ideal way to do this because it has little or no effect on the composition of the photo.

You simply need to change the shutter speed (or change the sensitivity to light – ISO) to compensate for changes in exposure due to aperture adjustments.

Changes in distance and focal length also affect DOF, but these changes have consequences in terms of composition. Thus, aperture changes are the best way to manipulate DOF without affecting the composition of a photo.

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