Back to Basics Photography: Depth of Field

The Secret Photography Ingredients to Getting Blurred Backgrounds

(Written by Amy Short via MCP Actions)

One of the things I see many photographers ask each other is, “How do I get that blurry background? That bokeh I see everywhere? What lens does that?” While we may not always want a blurred background, it can really help in situations where you want to provide a distinct separation between your subject(s) and the background. Well, it’s not just a specific lens, and there are a number of factors that can play into a blurred background. This may sound complicated, but once you understand all the factors, it’s really easy to start getting beautifully blurred backgrounds in your photos when you would like to have them.

Secret Ingredient 1: Depth of field
The first thing to understand when learning about getting a blurry background is depth of field. There are other factors, but depth of field (DOF) is a big one. Depth of field is the name for the depth (front to back) of your focal plane. What exactly is a focal plane? A focal plane is the amount of your photo that is in focus, and it is parallel to your camera’s sensor (and essentially the front of your lens). It theoretically goes up and down and side to side to infinity, but its front to back width, or depth, is finite based on the factors below. Think of it as a large sheet of glass that has a varying front to back depth depending on the factors below. All of the factors combine to create the depth of field of each shot. Can you actually see it? Well, you’re obviously not going to see a pane of glass through your photo but in some instances you can see the focal plane run right through the photo, like in the example below. It’s just a slice of focus.

Photo showing slice of focal plane through a photo

Secret Ingredient 2: Aperture
Aperture is one of the factors that impacts depth of field. The wider your aperture (smaller f number), the narrower your depth of field. This means you will have a very small area from front to back in focus. Conversely, the narrower your aperture (larger f number), the wider your depth of field will be. You will have a much wider focal plane from front to back. So a lens at f8 will have a much wider DOF than at f2.

Secret Ingredient 3: Focal length
The longer the focal length of your lens at a given aperture, the wider your depth of field will be. The longer your focal length, the narrower your depth of field. So a lens at 24mm will have a wider depth of field than a lens at 70mm, given all other factors are equal.

Secret Ingredient 4: Distance from subject
The closer you are to your subject, the narrower your depth of field will be. The farther away you are, the wider it will be. If you are at f4 at 70mm and are 4 feet away from your subject, your depth of field will be much narrower than if you were at f4 and 70mm and 15 feet away from your subject. This is also the reason why, with macro lenses, the depth of field is extremely thin, even with narrower apertures: because you are so very close to your subject. In the example below, I was at 70mm (a somewhat long focal length) and 2.8 (a fairly wide aperture; it was sundown and I opened my lens as wide as I could so as not to raise the ISO super high). These two factors point towards a narrow depth of field much of the time. However, my subjects that I focused on, those little surfers out in the water, were a good 50 yards away from me, so my depth of field was actually quite deep and there is relatively little blur or out of focus area in the photo except for a bit in the foreground.

Photo showing wide depth of field at a wide aperture

Some of the best advice I can give you is to play around with these three factors to get an understanding of depth of field. Take the same photo at the same focal length and the same aperture but get farther from your subject each time and see how your focal plane depth changes. Or, take the same photo with the same focal length and same distance from subject and narrow your aperture with each photo. You will be able to see how there is more in focus each time.

So how does this help me and how does this relate to a blurred background?
Well, first of all, understanding depth of field will allow you to understand what settings you need in getting your desired subject(s) in focus. You need to understand that if your focal plane is only 6 inches wide and you have three rows of people that are four feet deep total, your subjects are not all going to be in focus. This is a very important concept to understand. But also, since everything that is not in the plane of focus won’t actually BE in focus, it will be blurred. so, everything behind your focal plane (and sometimes in front, depending on how you frame and how wide your DOF is) will be blurred. The wider your aperture/longer your focal length/closer your distance to subject (or a combination of the three), the more blur there will be.
So, it’s that easy? There’s nothing else I need to knowWell, there is one more piece. And with blur, this is probably the most important part. That piece is the distance of your subject from the background. You could be shooting at a wide aperture and a moderately long focal length and be quite close to your subject, but if your subject is right up against a wall or bush or any background item, there is going to be little to none of that blur you’re looking for. You need to pull them as far away from the background as you can for the most blur.
In this example, I had two of the three factors that set me up for a narrow depth of field and set the stage for good blur: wide aperture and long focal length. I wasn’t extremely close to her but given my focal length I wasn’t too far either. What really dialed in that great background blur was how far she was from the background, though; approximately 200 yards. The long focal length makes it appear closer but all the other factors still give a nice blur.

An example of how subject distance from background can affect background blur

You don’t always need to have a wide aperture or super long focal length for a blurry background, though.  In my next example, which is actually straight from the camera, my focal length is shorter than in my last example, and my aperture is all the way up at 7.1.  So how do I get such a blur to the background?  Two factors:  one is that my subjects (my nail polish bottles!) are quite a distance from the green background.  The other reason is that I shot relatively close to my subjects, only about three feet away.  You can see in this photo, like the original photo in the post, the focal plane running right across the photo, on the deck board.

Photo that shows blur in background even with narrow aperture


Once you learn all the factors that come into play to get a nice background blur, it becomes second nature.  You can truly get blur with any lens, even kit lenses, so play around with all the factors mentioned above and see what you can do!

Amy Short is a Wakefield, RI-based portrait photographer. When she’s not working, she will photograph anything and everything. You can find her at and

Portraits by Bukool is a Cebu-based destination wedding photographer and is a recipient of several awards since 2012.
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