How to make your Photo Background Blurry

If you want to take your photography to the next level and get professional looking photos, understanding depth of field is a big key. Depth of field is what makes your background in your photo go blurry. This can be a little confusing so it will help if I go into some detail on how your camera lens works. Understanding how the lens works to let in light, will help you understand how to get the best out of your photography. So before I get a step ahead of myself, I would like to answer a simple question…

What is Depth of Field?

The depth of field is the area in your photograph that is in focus. This is controlled by your lens’s aperture. In your photo, if the area that is in focus is small, it is referred to as a shallow depth of field. To get a very shallow depth of field, you need to have a fast lens. Have a look at the example photo below. You can see that the area of grass in focus is a little strip in the middle of the photo. This means there is a shallow depth of field.

grass depth of field

If the grass was completely in focus from the foreground to the background, the photograph would have a large depth of field. Most camera lenses have the ability to do that.

So what is so great about a Shallow Depth of Field?

Shallow depth of field is best when photographing a portrait of one person or an object, but not so good when photographing landscapes or groups of people.

When taking portraits, it helps if your background is not detailed. A nice amount of background blur will make your subject stand out much more, and will bring them out of the image. If you are taking close up portraits, you can isolate parts of the person’s body you wish to emphasize. In the example below, the shallow depth of field first focuses on the models eyes and in the second shot, her face is blurred and the rings are what you focus on. This simply looks great!

goth_girl_dof

To photograph a landscape, you want as much of your photograph to be in focus as possible so you would use a larger depth of field by selecting a higher aperture number. This photograph of one of my favorite Auckland spots was photographed at f11.

beach_nite_DOF

What is Aperture?

To control the depth of field on your camera, you use the aperture settings. These are the settings on your camera that usually start with an f.

aperture_diagram

Inside your camera lens are little blades that form a hole that opens and closes to let in more or less light. Much like the iris of your eye does. The lower the aperture number you choose, the more light you let into your camera, because the blades open wide. This action of opening the iris (aperture) means that more of the lens surface can be used to take the photo. The side effect of using more lens surface, is that your depth of field gets shallower. The higher aperture number lets in less light, as the blades close the opening to a very small hole. Also less of the lens surface is used and your depth of field increases.
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a bride showing a shallow depth of field

A photo of a bride showing a shallow depth of field, which makes her nicely stand out from the background. If the bark of the tree was in focus, the bride would be a little lost in the photograph.

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Sharpness

A side effect of changing your aperture settings means that at each end of the spectrum, you lose sharpness in your photographs. I will cover this in another tutorial at some stage, but if you are after the sharpest images your lens can produce, you will want to shoot at an aperture between around f5.6 – f11. Or close to the middle of the aperture range of your lens.

Depth of Field in more, errr, Depth

Here, I have done a test, to completely show the effects of how the aperture settings on your camera can control the depth of field. When the aperture is completely open, only a small part of the photograph is in focus. The foreground and the background are nicely blurred which means you can isolate your subject. Once the aperture is closed down, the whole photograph comes into focus. Please note! To achieve this effect you need to be as close as possible to the objects you are photographing and you will get the best results with a fast lens. I used the Canon 85mm f1.8 for this demonstration.

The mighty retro cassettes photographed below at f1.8, shows the power of the fully open aperture, and a shallow depth of field. The blurred elements are smooth and the middle cassette is nicely isolated. It is important to note that because I was letting in a lot of light into the camera, I had to use a faster shutter speed so that my image would not be over exposed. As I progressively “stop down” to higher aperture numbers, I have to slow the shutter speed down to let in more light. Also there is a little purple fringing as a result of the wide open aperture.

cassette1p8_shallow

The cassettes photographed at f5.6, show that you can still get an ok amount of blur at a medium aperture. This gives you an average depth of field. If you are using the standard Canon kit lens of 18-55mm, you would want to be zoomed in to the 55mm end of your zoom, and be as close to your subject as you can, to get that background blur.

cassette5p6_avr

Now below, at an aperture setting of f8, you can see that the blur is almost gone. This would be around the sharpest point of this lens, and would be great for photographing landscapes or groups of people.

cassette8_avr

Finally below at the aperture setting of f16, you can see that any blur is practically gone. This would give you the ultimate large, or deep depth of field. This is great for landscapes, although at f16, you will start to lose just a little of your sharpness in your photographs.

cassette16_large

What is a Fast Lens?

A fast lens is one that has a lower aperture range. It is called a fast lens because it lets in more light, and that means you have to shoot at faster shutter speeds, to stop your photos becoming over exposed. Your average lens will range from a lower aperture setting of f3.5 – f5.6. The standard 18-55mm Canon kit lens has its lowest aperture reading of f3.5 when zoomed out. An example of a fast lens, is a fixed zoom (or prime) 50mm f1.8 that Canon has in its lineup. This is a sharp, cheap lens, that because of the low aperture, will enable you to photograph your subjects with a very shallow depth of field. We have seen that the shallow depth of field will give that pleasing background blur.

Flower_depth of field

Summary

Please feel free to email me if you have further questions on depth of field. The general rules that I try to follow are, if I am photographing one person, pet or object, I will try and get a nice shallow depth of field so I can isolate the subject from the background. That means I will use a lower aperture number like f1.2 to f2.8. If I am photographing anything else, where I want much more of the photograph sharp and in focus, I will use a higher aperture number like f8 to f11 (light permitting).

leaf_depth of field

Remember if you are going for that blurred background, the closer you are to your model or subject, the more the background will blur on the lower aperture numbers. Have a bit of fun and experiment with your lens and camera. Even if you don’t have a fast lens, you can get a little background blur if you are close enough to your subject, and you have your camera on its lowest number aperture settings. Also have a look through the portraits section of my site, and see where I have used a shallow depth of field, and when I have not. It might help you decide how to use it.
Most of all, take lots of photos and try and learn as you go. That is the best way to get better!



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