Recently in our Learning Community, there were some questions posted about how to get both dogs in focus, since the camera only ever seems to focus on one dog, or about how the paw of the dog AND the nose can be sharp, but not the eyes – when these two body parts are seemingly quite far apart from one another.
This is where a solid understanding of what depth of field and the plane of focus is.
Throughout the following lessons, we’re going to be focusing on and talking a lot about getting a NARROW depth of field – that is, a very small plane of the photo in focus – in order to get soft, blurry backgrounds for our portrait photos. But there are times you may want to manipulate that plane of focus to make it wider, or to know when you’ll need to take multiple photos and mask them together in photoshop, because the physics of the situation won’t let you have a wide enough plane of focus.
What is focus?
I think this is where most people get mixed up.
There is a belief that the camera focuses on a thing. A paw, a nose, an eye, and that focus is isolated to that one place, to the exclusion of everything else.
But that isn’t the case, and I’ll prove it.
Grab a photo where you can see some of the ground (eg., the ground isn’t obscured by blurry foreground). Where is the focus on the dog? Maybe the eye, maybe the nose, it doesn’t really matter.
Now look at the ground.
I’m willing to bet there’s a line of grass/gravel/leaves that is also as in focus as the eyes/nose/whatever of the dog.
Above, Loki’s eyes are definitely in focus, his nose is not, and yet there is a distinct line on the ground that is in focus, as well as a line of bushes on either side of the road.
Because, in fact, the camera focuses on a distance from itself, and the area that is in focus is a width which can be wider or narrower depending on the factors you’re about to learn about in this topic.
This area that is in focus (the plane of focus) goes front to back (or back to front) and anything that is in this plane, will be in focus, fading out to less and less in focus as you get closer to the camera, or further away.
Let’s look at a photo from above.
Imagine that we’re a bird looking down on the scene of Loki.
This is how our scene would look with no depth of field, no camera, just looking with our eyes.
If we follow the ideas laid out in the lessons you’re about to dive into, we will hopefully end up with a narrow depth of field/narrow plane of focus, which means a small width of the photo will be sharpest, with focus falling off as the scene gets closer or further away from that plane.
This is about the plane of focus shown in the photo above. Everything inside the two black lines as indicated by the arrows, will be in focus. So from above, it would look something like this:
Which is essentially what you see in the photo of Loki. Let’s do a side-by side. Can you see the line of focus on the ground and in the bushes?
If we were to change some things about our photo, namely:
- the aperture chosen
- how far away we are from the subject
- the lens we use
we would be able to change how wide this plane of focus is. You’ll be learning a lot more about these conditions in the lessons to come. Let’s have a look at a quick example of how the depth of field widens simply by changing the aperture of the lens. We’ll use some graphics as well with our birds-eye-view to help us see it. You’ll encounter these photos with full explanations in the aperture lesson, but for now I want you to pay close attention to the moss on the tree trunk, and the fur of Journey’s knee (back leg).
For the example graphics I’m using the same photo of Loki because Journey’s sleeping right now and I don’t want to disturb him. Just imagine it’s Journey, lying down.
This photo has a narrow depth of field, or a narrow plane of focus. You can see that the plane is probably only a few centimeters wide, from his snout to just behind his eyes. His knee and the moss in front are blurry. This was taken at f/1.8
This photo was taken at f/8, which has resulted in a much WIDER plane of focus. The plane is now probably 70cm wide, going from the moss almost at the very edge of the log, right to Journey’s knee and possible further back, we just can’t see it.
This is also a great example of how the focus doesn’t just stop and start (it kind of appears that way when the depth of field is narrow, because it happens very fast going from in focus to out of focus.) but that it goes gradually. Look at the background in both photos. In the top one, the plane of focus is already so far away by the distance of the background that it is super soft and blurry.
In the 2nd photo, the plane of focus and therefore the graduation of it going out of focus GRADUALLY, is wider, meaning the trees we see are more in focus, but the ones behind THEM are just as blurry as in the first photo.
Here’s the two images side by side. Again take note of the moss and the knee.
And yes, I realise that in the 2nd photo I was a bit closer to Journey.. but if anything that would make the plane of focus NARROWER than if I’d been further back, shooting at f/8
What this means for group photos
As mentioned at the start, there have been some questions lately in the Community about group photos.
Have a think about everything you’ve just learnt about the plane of focus. If you have two dogs sitting side by side, one 20cm forward than the one the camera focused on, what will this mean for your photo? Does it mean the camera has only focused on one dog, or that the 2nd dog is outside the plane of focus?
There will be another lesson on group photos in this Depth of Field topic, so don’t worry if you aren’t yet sure how to take photos of more than one dog, or of a dog and owner.