When you focus your camera’s lens onto something, that subject should come out nice and sharp in your photo. Things that are further away or closer to your camera won’t come out looking as sharp though.
In this photo I’m pointing a red arrow to where I was focusing. Like you’d expect it was inside the region that came out sharpest in the photo.
You’ll see that a short distance beyond the arrow and also a short distance on this side of the arrow things start looking fuzzy. That kind of thing is normal because you can’t focus on all parts of the scene at the same time.
You’ll also notice that everything the same distance from the camera as the arrow is also looking sharp, because when you’re focusing on something what you’re really doing is focusing your lens on a certain distance away from your camera.
In this next example, I’m focusing on the same bit of text, but a much bigger range of stuff extending closer to the camera and also beyond the subject came out looking sharp.
You’ll notice that things still start looking blurry as you get further away beyond the arrow, or closer to the camera from the arrow, but not nearly as blurry as the first example. The distance from the arrow to where things look fuzzy is greater.
The difference between those two photos is that the second photo had more depth of field.
So, here’s my definition for depth of field:
It’s the amount of distance between the closest and farthest things looking sharp in your photo.
If things look sharp through a big distance, from right up close to way off in the distance, then your picture has a big depth of field.
Here’s another way of looking at it. The graphic above is depicting a big depth of field alongside a small (or shallow) depth of field.
Depth of field is a lot more than just some sort of academic thing. The truth is that it has a huge effect on how a photo looks. For example, in these photos of the kangaroo paw flower the only thing I changed was the depth of field, and the resulting pictures look very different.
Personally I prefer the look of the flower with the blurry background. And this is why it’s great to look past the automatic settings of SLR cameras, because it allows you to make creative choices like how much depth of field you want instead of just letting your camera make all those choices for you.
In the examples I gave above I had the same bits in focus (looking nice and sharp) but I had different amounts of depth of field, so you can see that depth of field is not the same thing as focus.
The good news is, it’s really easy to manipulate how much depth of field you get in your shots (hint: aperture). I explain all about it and a heap more in my starter’s guide.