Focus in Photography
Focus is one of the biggest pillars of photography since the very first day someone used a camera to capture an image.
We could discuss about composition, settings, HDR, bracketings, stackings and plenty of other things, but without a decent knowledge about focus, none of these arguments will make any sense.
To some of you, focus at a first glance could even look like a trivial argument, something that it’s so obvious and easy that there’s no need to write a whole article about it. I can tell you that you have never been so wrong! It’s neither easy nor obvious: it will take you quite some time to really master the focus and have a great knowledge about it.
The aim of this article is to give you as much informations as we possibly can about focus, from what is it to the different ways of use, from the practical applications till the more complex techniques of focusing (e.g. the hyperfocal).
1. What is Focus?
Technically speaking, focus is the result of a combination of your lens aperture and light: to make it easy, depending on how light rays are converging into your lens and what kind of aperture you have selected, different parts of your image will be in focus.
Smaller apertures (like f/8 - f/11 - f/16) will “force” all the light coming from outside to pass through a tiny hole and concentrate on the image sensor: as a result, a bigger part of the image will be in focus. On the other side, wider apertures (like f/1.4 - f/2.8 - f/4) will spread all the light rays on a bigger part of the image sensor, since the hole I mentioned a few lines above is now much bigger: this will result is a photo with a smaller “depth of field” (we’ll talk about it later).
Practically speaking, you can check whether a picture is in focus or not by its sharpness: the sharper it will look, the more it will be in focus. Be careful though: sometimes photographers choose to highlight or hide some parts of the image through the use of focus, so it may be normal to see some out of focus areas as they visually enhance more the sharp parts. I guess that’s what we call “the artistic side of photography”!
2. Focus Settings on the Camera
So, now that you know what focus is, it’s time to put those informations to good use by taking your camera into your hands and start experimenting! In this big chapter, we’ll see together how different focusing methods works and which one of them works best in different kinds of situations.
2.1 Camera Focus Modes
On pretty much every camera model available on the market, you should have at least three choices when it comes to the focusing method: AF-S, AF-C, and manual focus. In other words, you’ll have two different options (actually, more than two, but we’ll talk about it later) for the autofocus and the remaining one is the good old manual. Let’s discover each one of them!
2.1.1 AF-S (Single Shot)
AF-S is the autofocus mode which allows you to lock the focus on the subject you’ve chosen, and then you might move (or not) from there and recompose the photo as you wish. The single shot autofocus is the ideal way to capture still and slow moving scenes: it will be the faster way to focus on a subject and so the faster way to capture the shot. AF-S works perfectly with street photography, portraits and event photography, just to name a few. All the scenes where you have the time to re-focus between one shot and the next one suits the AF-S mode.
On the other hand though, it’s not ideal for fast moving subjects, where instead AF-C comes in handy.
2.1.2 AF-C (Continuous Autofocus)
AF-C fills the gaps of the single shot autofocus: by choosing the continuous autofocus mode, your camera will automatically refocus on your subject each time it moves, just by keeping the shutter button halfway pressed.
No need to say that this focusing method works great with fast moving subjects: since you’ll never lose the focus on your subject, you can follow and track him without having to refocus everytime you take a shot. Sports photography, action photography and wildlife photography are just a bunch of the genres amongst where continuous mode is really popular and can make a difference.
2.1.3 Manual Focus
The last focusing method of this list happens to be also the oldest one of them all: the manual focus. In this case there are no camera processors, no autofocusing motors or any other external help: it will be just you and your ability to peak the right focus to get a perfectly sharp subject.
Still scenes are generally the situations that suit more the use of manual focus, even better if you could use a tripod.
Landscape, studio and macro photography are just a few of the genres where manual focus is more popular: what they have in common? These are all photography genres where (generally, at least) you have the time to check if you manage to get the right focus and, if not, re-focus again.
Focus stacking anyone?
Already know the basics? You might want to give a read to this guide on focus stacking then!
2.2 Autofocus Area Modes
Now that we discussed about the various focusing methods, it’s time to talk about the different areas that you can select when autofocus is in use. All of the most recent cameras should have at least three choices when it comes to autofocus areas: the single point autofocus, the dynamic area and the auto area autofocus. Let’s see what are the main differences between them.
2.2.1 Single Point Autofocus
When the single-point mode is chosen, by looking inside your viewfinder you’ll be able to select just one small rectangle out of the many that are present in the focus area: this is generally the precisest way to focus on your subject, specially if it covers a small part of the frame or you want to focus on a particular part of it (e.g. the eyes).
2.2.2 Dynamic Area Autofocus
By selecting the dynamic area mode instead of the single-point one, when you’ll check the scene through the viewfinder you’ll see multiple focus points selected at the same time, and not just one. The number of the selected points will mostly depends about your camera’s autofocus capabilities; sometimes though, you get more than one option in order to select how big that area you want it to be (8-focus points, 21-focus points, etc).
This autofocus mode works greatly when you are shooting big subjects or you want wide areas of the frame to be in focus; it’s not the best option instead when precision is required, as the single-point AF works better in those situations.
2.2.3 Auto Area Autofocus
As the name suggests, this is the most automated way to autofocus, since the camera will not just limit itself to focus, but it will also choose where to peak the focus! It may sound super cool and easy at first sight, but truth is that it has a few annoying limitations. In low-light situation the autofocus is already struggling by itself, and when it has to choose also the area where to focus, it may not be able to do it at all. In low contrast conditions, where the main subject is not standing out from the background, it may have some problems to choose the right focus.
Personally, I’d recommend to use this auto-area autofocus with fast moving subjects, where you don’t have the time to select the autofocus point (or area) by yourself and you have to rely on your camera.
2.3 When to Use Manual Focus/Autofocus
As I already wrote earlier while talking about camera focus modes, each focus method will suit best just a few photographic genres, while it won’t be recommended for others.
Generally, we use manual focus for static scenes, the ones where you have time to settle down and re-focus if there’s the need, while we use the single-shot autofocus for slow moving scenes and the continuous autofocus for fast moving situations.
As you may have understood by now, the main variable when it comes to choose the right autofocus mode is the time you have at your disposal to take that picture.
2.4 How to Combine Camera Focus Modes with Autofocus Area Modes
Could you imagine shooting an automotive race with the manual focus? I think we can all agree that it would be close to impossible to peak the right focus. On the other hand, think about doing a focus stacking in macro photography with the continuous autofocus: you would go crazy over selecting the exact focus point each time, and probably the autofocus wouldn’t peak the right spot by itself. Now I’ll give you a few tips about what focus mode (and autofocus area) would be better to use with some photography genres.
Last time I checked, landscapes and buildings don’t move. And even if there are some dynamic elements in your frame (clouds, waves, etc), 99% of the times you’ll have enough time between one shot and the next to re-focus in case something went wrong with the previous one. That’s why in landscape and architecture photography manual mode (or AF-S in cash you don’t have time) is generally recommended.
- Still People
In this specific case I’m going to consider just still people, so mainly portraits and a few street photography situations. Which focus mode you’ll have to use will mostly depend on how much control you have over the situation: if you are shooting in a static environment with your own model, you may as well use the manual focus to peak the best point in the frame (spoiler: you might want to focus on the eyes). If you don’t have much control over what you are shooting instead, you better choose the AF-S mode, with the single point or dynamic area modes selected according to where your subject will stand in the photo and how big it will be.
There’s no other way to say this, so I might as well avoid any useless speeches: 99% of the times you’ll shoot any sport or action scene, you’ll have to use the AF-C (continuous autofocus mode) with the dynamic area or auto area modes, depending on how fast your subject is. That’s the best way to shoot sports!
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2.5 Back Button Focus
The back button focus is a smart trick underestimated by many photographers; you’ll generally find this button near the viewfinder on your camera.
Let’s start from this: how do you generally autofocus? By half-pressing the shutter button, right? Then, if you got the focus right, you press a bit more and take the shot. The back focus button is basically doing the first part of the aforementioned process: you’ll be able to separate the focus and the capture parts. In this way, if you want to maintain the focus locked on the subject, you won’t have to change the focus points every time you re-compose, you’ll just need to press once the back button to block the focus.
3. Depth of Field
We already encountered the words “depth of field (dof)” earlier, when talking about what is focus. Depth of field is one of the major concepts of the photography universe, so you’ll need to make sure you perfectly understood how it works and what it is in order to improve your skills.
To understand what is the depth of field, you’ll need to know first what is the so-called “focal plane”: in a few words, it’s the point where the focus is falling. Imagine for a moment your picture in three dimensions: you’ll be able to select (virtually) endless focal planes in there.
Now, let’s talk about the aperture of your lens: at wider apertures, since the light rays are spreaded all over the sensor, you won’t be able to put in focus many focal planes, while the opposite will happen when you’ll use smaller apertures.
In photography terms, when you use wide apertures you’ll get a narrow depth of field, while with small apertures you’ll get a big depth of field. It may feel counterintuitive at first, but after a while you’ll get use to it!
In poor and simplistic words, depth of field is the amount of focal planes that you manage to get in focus given a specific aperture.
4. Hyperfocal Distance
The first reaction of many people, when the first discover the hyperfocal distance, is thinking that this is some kind of magical technique that will give them the “power” of having everything in focus from the close foreground till the far background. In every, possible situation. At all times.
Let me give you the bad news: it doesn’t work like that (unfortunately). Don’t get me wrong, hyperfocal distance can come in handy, sure, but to give you an idea I never used it once in the last 5 or 6 years. And well, I took quite a few pictures in this time window!
For start, let me explain what it is, for those of you who don’t know: the hyperfocal is a specific focusing distance where you’ll have all the objects from half that distance till the background enoughly sharp. This distance changes everytime that you modify the aperture of your lens and/or change the focal length at which you are shooting. Starting to feel quite tricky, isn’t it? Don’t worry: there are plenty of hyperfocal calculators both online and in app stores, so that you won’t have to do the maths each time but you’ll just need to re-focus at the distance given by the calculator.
Hyperfocal distance can be useful when you are shooting in low light conditions but still needing a big depth of field (e.g. night photography). In case you can’t get everything in focus with the hyperfocal distance (or you don’t feel it’s sharp enough), focus stacking could be the solution to your problem: it’s another helpful technique (a little more complex) that consists in taking multiple exposures with different focus points, and then merge them together in post production.
5. Focus vs. Depth of Field vs. Sharpness
Let’s make a small sum up about what we’ve learned so far: the three main subjects of the article are focus (obviously!), depth of field and sharpness. We talked quite a lot of first two, while I barely mentioned sharpness all along the article: let me explain why.
Focus is an objective measurement: a picture whether it’s in focus or it isn’t, there’s no such a thing as “it’s in focus in my opinion”. It’s the spot of the frame that has the maximum sharpness.
Depth of field too, even if it’s a bit more complicated that the focus itself, it still is an objective measure: hard to precisely calculate in terms of numbers on the field, easier to naturally perceive where it starts and where it ends.
Sharpness instead is the less objective measurement out of the three: that’s because we perceive a photo as sharp or not, but there’s not a way to precisely measure the sharpness of an image. Let me make an example to explain myself better: when observing a photo with a large depth of field (e.g. landscape) our eyes instantly look for sharpness everywhere, and we wouldn’t be pleased to see the foreground slightly blurred or the background not razor-sharp. In a case like this, we generally look for an equal degree of sharpness everywhere in the frame. On the other hand, try to look at a portrait photo taken with a really wide aperture: just the most important part of the frame (e.g. the eyes) would be in focus, while the rest would be blurred. Our eyes would still pleased and consider it razor sharp, even if 95% of the photo are out of focus. And I won’t stop here: the out of focus parts of the picture will give us the feel that the area where the focus is falling looks sharper than it actually is. As I said in the first place, sharpness is for a good part subject to our perception.
A very general and somewhat inaccurate statement can be that the more a picture is in focus the sharper it will look and when gradually getting out of focus it will become less sharp too; the larger depth of field a picture has, the less sharp it will look, will the opposite will happen with a narrow depth of field. Again, take this as a brief and simple way to explain the correlation between these variables!
6. Common Problems with Focusing and Solutions
What I avoided to write in the previous chapters is that focusing sometimes will give you an hard time. And I’m not just referring to the autofocus, but also manual focus will be difficult under certain conditions. Let me help you by giving you a couple of tips for when you won’t manage to get the focus right!
- Low light conditions: one of the most common situations where focusing won’t be easy is when you are shooting with low light. Some cameras/lenses will perform better than others, but they will all fail below a certain degree of light; cameras won’t be able to autofocus in darkness, and neither will you!
Live view will come in handy as a solution since you’ll be able to zoom into the scene and try to get the right focus; if it’s too dark and you can’t see a thing from the live view of your camera, you might want to light up some of the subjects (with headlight, torch, lamp, etc) and check the live view again to see if now you are able to properly focus.
- Fast Moving Subjects: we already talked about this in one of the first chapters, but fast moving subjects will be a pain in the back to focus, trust me. The best possible way to frame them and getting the focus right is using the continuous autofocus with the auto-area mode selected in case you are standing still with your camera, while the dynamic area mode selected in case you can track and follow them by moving your camera.
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