Whether you want to film a tennis match or take a close-up of a butterfly, you will need the right lens. Several criteria need to be considered:
• Focal length
• Field of view
• Maximum aperture
Depth of field describes the area of a scene that is considered in focus. It is influenced by several factors, but it is mainly related to the aperture of your lens at the time of shooting. One of the first things for a beginner in photography to understand is how to correctly choose an appropriate depth of field for your shot. Let’s see what depth of field is, the factors that influence it, and how to use it in photography.
How aperture affects depth of field?
The aperture of a lens is the physical size of the hole that allows light to pass through it and reach the camera’s sensor. Lenses contain aperture blades that can be controlled to adjust the size of this hole.
The size of the aperture is measured by an f-stop value.
- A low f-stop number (such as f/2.8) corresponds to a large aperture, allowing a lot of light into the camera.
- A high f-stop number means that the aperture is narrowed, and less light is allowed into the camera.
But then, why would you want a small aperture?
Without going into the physical details of how it works, a high f-stop number allows for a greater depth of field. So, a smaller aperture in the lens means that a larger part of the scene is in focus.
It is evident that you cannot shoot at f/22 all the time – there is rarely enough light for that. Even if there was enough light, you will find that the image suffers from what is called diffraction and may appear less sharp than expected. Anything beyond f/20 will likely experience the effects of diffraction.
Additionally, many photographers strive to achieve a blurred effect in their images. This is called bokeh! Bokeh describes the areas of an image that are out of focus, and generally, a shallow depth of field (small f-number) means that you will see a larger and more beautiful bokeh in your shot.
But you don’t need to constantly fight for a shallow depth of field. Sometimes, you can capture much more interesting photos by incorporating the environment into your image. A high f-number (small aperture) can bring the background into focus and create a more dynamic image.
Landscape photographers spend more time at higher f-stop values. They want the entire scene to be in focus, while portrait photographers generally want to focus attention on their subject.
Camera-to-subject distance and depth of field
It is not only the aperture of your lens that affects the depth of field in your images. The distance from your camera to the subject also has an impact.
- The closer you are to your subject, the shallower the depth of field will be.
- The farther away you are from your subject, the greater your depth of field will be.
However, there is a limit. The depth of field extends both in front of and behind the focal point, so if you focus at infinity, you will end up with less of the scene in focus than if you focused on a point closer to the camera. This is because the depth of field “falls off” beyond infinity. To understand this well, you need to focus on the “hyperfocal distance.”
Depth of field and focal lengths
Without going into details, a longer focal length results in a shallower depth of field. Therefore, you will generally get a greater depth of field with a wide-angle lens than with a telephoto lens.
How to achieve “good” bokeh ?
For portrait photographers, among others, you will certainly want to know how to achieve good bokeh. Based on the points above, you know several ways to create a shallower depth of field. This is essential to achieve a “good” bokeh effect. A shallow depth of field makes a large part of the scene blurry, and the elements in the background are more likely to form soft and pleasant textures.
It is important to ensure that you have a wide aperture (low f-number) and be as close to your subject as possible. You also know that the longer your focal length, the shallower your depth of field will be. That’s why it is best to use a telephoto lens with a wide maximum aperture (it is often said that such a lens is “fast”).
The subject-background distance also matters, and you will also notice a better bokeh effect if the background behind your subject is further away. This means it is further from the plane of focus and therefore more blurred.
We hope that you now have a much better understanding of depth of field and how it affects your photos. The key to photography is creative experimentation; play with your settings and see firsthand how things change. Whether you prefer a shallow or a large depth of field, it’s up to you to choose.
When taking photos, consider the reasons why you choose one or the other, and you will quickly find that you can adjust your settings correctly and easily.