People often ask me, “What is a bokeh background in photography?” and the following question is always, “How do I achieve bokeh background in my photos?”.
In photography, one of the most appealing effects to reproduce and play with is to create a photo with a soft background blur. But how to do it?
A blurred background, commonly known as bokeh effect, is obtained by controlling a series of aspects such as aperture, distance from the subject, focal length, and sensor size. In this article, I’ll walk you through this technique step by step. By the end of it, you’ll be able to obtain a beautiful bokeh background.
Let’s dive into it.
What is a Bokeh Background?
Bokeh is the term used in photography to describe the optical phenomenon of a soft out-of-focus background. It’s a Japanese word, and it means “blur” or “haze”.
It’s such an essential aspect of photography because it can dramatically change the viewer’s perception of the subject.
When out of focus, highlights areas of the image become soft and ghostly circles of light, delightful to the eye.
Bokeh determines how much a subject (object or person or animal) in a photo stands out from the background, and it helps to enhance the 3-dimensional feel of the image.
Depending on the lens, bokeh can have various shapes.
It can be circular, or even hexagonal. The edges of the circles can be smoother or rougher.
And all this can affect the appeal of an image.
In this article, I’ll see me use the terms background blur and bokeh effect interchangeably.
How Aperture Affects Bokeh
As you may or may not know, the aperture of a lens can be wide or narrow. It determines the quantity of light that reaches the camera sensor, and it’s measured in f/stops.
A wide aperture can be, for example, f/2.8 or f/4 (or even less), while a narrow aperture is f/22.
The smaller the f/stop value the wider the aperture and vice versa.
So how does aperture produces bokeh?
If you set your camera to the maximum aperture (f/1.8 for example) the depth of field will be shorter.
The depth of field is the area within two points of acceptable sharpness in a photograph. Ah, easy!
So often, we are tempted to choose the widest aperture to achieve the maximum background blur, but depending on the scene, this could be a mistake.
You can obtain more aesthetically pleasing effects if some detail is left in the background to let the viewer understand or imagine the shapes surrounding the main subject.
If there’s too much detail, there wouldn’t be enough separation from the background, and the image will look two dimensional and confusing.
Distance From the Subject and Bokeh Effect
Minimizing the distance between yourself and the subject in your photos is another way of obtaining an excellent background blur.
When you are very close, the lens will focus closer, and the depth-of-field will also be shallower. You can also do a quick experiment with your eyes.
If you bring your finger very close to your nose and stare at it you’ll notice how the background gets blurrier.
So if you are shooting at 2 meters far from your subject, it’s not the same as being 50 or 70 cm (20″ or 30″) away from it.
Moreover, you might have noticed that the further away is the background from your subject, the easiest it is to obtain a good bokeh. The reason for this is because the depth-of-field is not a hard-line, after which everything is out of focus.
The DoF gradually fades from sharp to blurred.
A background very close to the main subject will make the bokeh less evident, and the quality of your image will suffer.
The final image will result in a messy composition without clear separation between the subject and its surroundings.
Focal Length and Background Blur
Despite the name, remember that focal length is not the length of a lens.
Technically, focal length is the measurement of the distance from the lens’s optical center to the sensor in the camera when the lens is focused at infinity.
It’s described in millimeters, it tells you the angle of view, the magnification, and it affects the depth-of-field.
The longer the focal length is, the shallower the depth-of-field will get (more bokeh).
The shorter the focal length, the bigger the depth-of-field (hence less bokeh).
Zoom lenses will be more versatile than prime lenses. Since the former have a variable focal length and you can play with it to achieve your optimal bokeh.
Prime lenses, anyway, tend to have a wider aperture (f/1.4 to f/2.8).
A long focal length (e.g., 300mm), such as the one of a telephoto lens, will compress the perspective and make the background look closer to the foreground.
At the same time, at the right aperture, will make the background so smooth, and it will isolate the main subject for a better result.
Sensor Size and Bokeh Effect
While the fierce “battle” amongst photographers about the impact of your camera sensor on image quality goes from the “bigger sensor is better” to “portability over resolution”, I don’t want to start yet another debate on this.
Sensor size has no questions an impact on image quality.
A bigger sensor will give you a higher dynamic range and better high ISO performance.
There’s no doubt that a bigger sensor will also help you deliver a smoother and creamier background.
But it’s unfair to say that small sensor cameras such as Micro Four Thirds systems or APS-C sensor are not able to achieve excellent bokeh.
You just need to know your tools, your camera, and your lenses. If you look at the following images, what do you see? Isn’t that a good bokeh? Well, they’re all images taken with a Micro Four Thirds sensor camera.
You might be interested in my review of the Olympus OM-D EM-1 Mark II.
And here’s the Review of the M.Zuiko 40-150mm PRO F/2.8 lens with which I took those photos. Let me know what you think.
Lens Quality and Bokeh Effect
It, of course, also depends on the quality and construction of the lens, and you might have heard photographers ask, “How good is the bokeh of that lens?”
As we’ve seen, increasing the focal length helps decreasing the depth-of-field (DoF) and create a smoother background for a more pleasing bokeh effect.
Though this also depends on the quality of the lens. Different lenses with the same focal length will give different results depending on their optics.
The number of blades that make up the aperture of your lens make the difference between different lenses. In less expensive lenses, you can find 5 or 6 blades, whereas better quality and pro lenses have 9 or more blades on the aperture.
Another factor to consider is the shape of the blades and how they are positioned.
A rounded aperture will always produce a better bokeh compared to an aperture with hard corners.
See it this way. The shape of the aperture’s blades will determine the shape of the out of focus area in your image.
So your bokeh will either be hexagonal or more or less circular.
A lens also has to be fast. An aperture of f/2.8 (or less) is more likely to produce a better effect than an f/8, because the wider the aperture, the shallower the depth of field.
In Conclusion, How do I Obtain a Good Bokeh Background in a Photo?
Ultimately, we’ve seen how a blurred background or bokeh is a nice component of a particular type of photographs.
It helps to highlight the main subject and making the image look more three-dimensional.
Bokeh depends on several factors, and I invite you to take your camera now and start experimenting with the points we’ve discussed above one by one.
Start playing with the aperture of your camera.
Set it to aperture priority. It’s called mode A (or Av on Canon cameras).
By starting from the smallest f/stop value, you will see how changing it will give you different results.
Then always using A mode, move away from the subject and then get closer to it. Move around and frame the main subject (person, animal, flower, or any object) in such a way so that the background is further away and again, compare the different results.
Add, in the end, the focal length factor.
If you have access to a telephoto zoom lens, start from the maximum focal lens.
Choose a distance from you and the subject and maintain it. Similarly, choose a distance from the subject you want to photograph to the background and keep it always the same.
Now, gradually decrease the focal length until you reach the optimal length for the aperture value that you are using.
You’ll be able to produce a wonderful bokeh in no time!
I hope that I answered your question about how to blur the background of a photo!
Don’t hesitate to ask me questions in the comments below and share with me your thoughts and your images.
I want to see what are your results!
Stefano Caioni is the founder of Pixinfocus. His passion for photography helps him discover new places and live new adventures.