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6. Aperture

What is Aperture?

Aperture means the opening in the lens. It looks like the image below:

Don’t worry about the symbols and numbers for now. Just know that this opening can change in size. To understand where it is located in the lens, see the image below:

Now have a look at the first image again.

You can see that aperture can open up or close down, just like some kind of a cool looking circular gate.

In the last section, we learned how to change the various settings in the manual mode.

When it came to aperture, we saw that the value looked something like a number preceded by the alphabet ‘f’, for example, f8.

Now is the right time to understand what this value means.

This value refers to the size of the opening of the aperture. The bigger this value, e.g. f22, the smaller the hole. Conversely the smaller this value, e.g. f4, the bigger is the aperture hole.

Sounds confusing? No problem, have a look at a more elaborate image:

You can see that when the number next to f is small, the aperture is wide open. And conversely, when the number next to f is big, the aperture starts to close down and becomes narrow.

It can sound confusing because if you notice, the relationship between the value and the opening is an inverse relationship. Smaller the number, bigger the opening. Bigger the number, smaller the opening.

This aperture value is referred to as the f-stop number.

So in the image above, the aperture opening was open the widest at an f-stop of f2.8, and was most narrow at an f-stop of f22.

By now we know that a camera works by taking in the light from the surroundings. We also learned that light first enters the lens.

Light is allowed to enter the lens by this aperture opening that we have been talking about.

So can you guess what will be the relationship between the light entering the lens and aperture?

Relationship Between Aperture and Light

Yes you guessed right! The wider the aperture is open, the more the light that enters the lens and the camera.

Conversely, if the aperture opening is narrow, lesser light enters the camera.

We can also say that a smaller f stop number, like f2.8, results in more light and a bigger f stop number, like f22, results in lesser amount of light.

So can you guess, at what aperture, will you have a chance of getting a very bright photograph?

Yes, you guessed it right. At a smaller f-stop number. Because the aperture will be wide open and will allow a lot of light to come in.

Conversely, when the f-stop number is big, the aperture opening will be narrow, so lesser light will be allowed to come in the camera. So chances of a darker shot are higher.

In photography, we use the term exposure to refer to the brightness. An underexposed photo is that which is dark, and an overexposed photo is that which is too bright.

So now you know the relationship between aperture and light.

Before we move on to the next part, I Just want you to change the aperture setting once again just to get comfortable with it.

So make sure your camera is on manual mode. Then, as seen before, press the (+/-) button and simultaneously, rotate the command dial. You’ll see the aperture value changing.

Now to be honest with you, this relationship isn’t of that much importance for us right now. What is very important for us, is the next relationship that we will be talking about because that will actually show you what aperture does to a photograph.

Relationship between Aperture and Depth of Field

I know what you’re thinking – What on earth is depth of field?

Don’t worry one bit. It’ll all be clear very soon.

First, I want to ask you a question.

Let’s assume there are two photographers – one who is just learning photography and another one, who has been shooting professionally.

They are both asked to take a shot of a person who is standing in a garden, with a lot of trees behind her in the background.

Let’s assume both these photographers take shots.

What difference are you likely to observe in both the shots?

Apart from the basic differences like the shot being sharper and other things, one major difference you’re likely to observe is that good photographers always manage to blur the background.

Because they know how to blur the background, their images look much better as the subject in the picture seems isolated from the background.

In addition to that, the distractions in the background are reduced because the background is blurred.

All this makes such a shot look very pleasing to the eye.

Let’s look at the scene we just talked about in terms of actual images.

Let’s first look at the image an amateur photographer would take:

You can see that the background is visible. This makes for a shot with a lot of distractions as there are a lot of things that are seen in the background.

Now let’s look at the image a professional photographer would take:

In this image, you can see that the background is blurred. Since you can’t see anything in the background, the eye naturally goes straight to the subject of the photograph – in this case, the woman.

This blurring of the background is done by using the aperture.

Let’s get into how all this works.

Let’s try and look at the pictures above in the form of a diagram to understand this:

If we convert the first photograph into a diagram, it would look something like this:

You can see that area of focus (pink area) extends from in front of the model to all the way beyond the tree in the background. That is why everything in that picture was in focus. The model was not isolated.

Now let’s take a look at the second shot. It was something like this:

Now you can see that the area in focus is very small. It’s only in and around the area in which the model is standing. So the model would be in focus, but the background behind will be blurred as it’s out of focus.

This area of focus that we are talking about is called as depth of field. It develops around the subject on which we lock focus before taking the shot.

A shallow depth of field refers to the situation in which the area of focus is small, just like the second shot and diagram.

A deep depth of field is the opposite. It refers to the situation in which the area of focus is big, just like the first shot and diagram.

So if you think about it – if we want to blur the background in any shot, our job is to learn how to achieve a shallow depth of field or a smaller area of focus. Once we are able to do that, everything that does not fall within the area of focus will come out blurred.

So how can you control the amount of depth of field or area in focus?

You can do it by using the aperture.

So what’s the relationship between aperture and depth of field?

It’s a simple relationship.

The smaller the f-stop number, the more shallow the depth of field or lesser the area in focus.

Conversely, the bigger the f-stop number, the deeper the depth of field or more the area in focus.

For example, at f4, lesser area will be in focus than at f16. Hence, at f4 we will be able to blur the background more as compared to f16.

At this point I will advise you to not think of this relationship in terms of the size of the aperture opening as it can end up confusing you.

Just think of this relationship with the f stop number as it’s much easier to understand.

Smaller the f-stop number, more blurred the background. That’s what you have to remember.

So at a smaller f stop number, only the object that you lock focus upon will be sharp as the depth of field will form around that object. Anything away from it will start to blur out.

This will become clear when we do a small exercise.

Exercises for Aperture

Exercise for Shallow Depth of Field (Blurring the background)

Here’s what I want you to do.

Take the cup you used for the last shot and place it in front of you on a table.

We’ll be taking a shot of this cup again, but this time remember, we’re on the manual mode.

And unlike last time, this time we have a major objective in front of us – To blur the background and the keep the cup sharp.

So let’s get started.

Since you want the background to come out blurred, the first thing you would do is to change the aperture value to the minimum f-stop number possible.

Now through-out this e-book, we’ll assume that you are using the kit lens that came with your camera, which is the 18-55mm f3.5-5.6 lens.

Whenever you see the aperture setting written next to the name of the lens, it denotes the minimum most f-stop number that lens is capable of going.

Better (and usually more expensive) lenses can go below f3.5. A lower f-stop number is very important because first of all, as you learned, it is capable of reducing the area of focus or depth of field even more, hence blurring the background more.

Secondly, as you also know, the lower the f-stop number, the wider the opening of the lens. This lets in more light in the camera, something which is very important as you’ll learn in the future chapters.

For now, just remember that the smaller the f-stop number, the better it is as it helps us to blur the background effectively.

So what is the minimum f-stop number that we can go to on our kit lens?

See the name again: 18-55mm f3.5-5.6.

This means that the lowest f-stop number that it can go to is f3.5 when the lens is zoomed out at 18mm and f5.6, when the lens is zoomed in at 55mm.

And anything in between, you’ll get a corresponding f-stop value that will be between f3.5-f5.6.

Slightly confusing? No problem.

In order to understand this practically, do the following:

  1. Zoom out using the zoom ring till you are on 18mm
  2. Reduce your aperture f-stop value to f3.5
  3. Now, zoom in and go to 55mm.
  4. You’ll notice that the f-stop value goes up on its own to f5.6.
  5. Again go back from 55mm to 18mm and you’ll see that the aperture has gone from f5.6 to f3.5. (On Canon cameras, sometimes you have to half-press the shutter button to see this change)

See the video below to watch the above steps:

Video 9: The effect of zooming in and zooming out on the aperture

Nikon users, click here to watch the video

Canon users, click here to watch the video

So this lens doesn’t have a fixed minimum f-stop number. Instead, it has a range of minimum f-stop number which depends on whether you are zoomed in or out.

Better (and usually more expensive) lenses can have a fixed f-stop number. For example, one the very popular lenses, the 70-200mm f2.8 has a fixed minimum f-stop number, which is f2.8. So in this lens, even if you zoom all the way in to 200mm, you can still use f2.8.

Does all this still sound confusing?

If it does, don’t worry a bit. As long as you have understood the relationship between aperture and blurring, we’re good to go. So just remember, lower the f-stop number, more the blurring. Rest of the things will fall into place when you start using the camera.

Let’s begin the exercise now.

Watch the video below to see what to do. Alternatively, you can read the description too.

Video 10: Blurring the Background Using Aperture

Nikon users, click here to watch the video

Canon users, click here to watch the video

  1. First of all, place a cup on a table in such a way that there is some background behind it, like shown in the image below:
  2. Next, make sure you are in a well-lit room.
  3. Next, make sure you are zoomed out all the way to 18mm.
  4. Rotate the command dial to change the shutter speed to 1/60. You don’t have to understand why we did this right now. You’ll understand it later on in the chapter on shutter speed. Similarly, change the ISO to 3200 (If the shot you get at the end of the exercise comes out darker, you need to raise the ISO value a bit. Conversely, if it comes out very bright, you can reduce it a bit). You’ll be able to understand this in the ISO chapter later on.
  5. Since we want to keep the cup sharp and blur the background, make your f-stop value f3.5.
  6. Now you may think you are ready to take the shot, but just hold on for a moment. There are three important steps that we have to follow to make sure we get a good shot:First, make sure the immediate background behind the cup is far away from the cup. There should be nothing immediately behind the cup. Let the background be a few feet away from the cup like you can see in the image above.The second thing to remember is that you should try and shoot in such a way that the camera is line with the cup. That means you can either keep the camera on the table or bend down a bit so you can go lower. But avoid shooting from a completely up-to-down angle. The reason for doing this will be explained after you take the shot. Again, see the image above for a better understanding.The third thing to remember is that you should go as close to the cup as possible. You can do this either by physically going close or zooming in. Going away and zooming in is always preferable as you’ll learn later on in the Portrait Photography chapter. Zooming in from far also solves the problem of the lens not being able to focus when the subject is very close to the lens as we saw in the first shot we took. So your job should be to zoom in so much that you can make the cup appear very big in the frame (on your LCD screen in live-view). There should not be too much empty space around the cup. Again, the reason for doing this will be explained after you take the shot. See the image below to get a better understanding:
    Now, we’re all set to take this shot. Make sure your focus mode is set to AF on your lens. Next, make sure the focus point is touching the cup as the cup is our main subject, just like shown in the image above.Next, half-press the shutter button to lock the focus. Once the focus is locked on the cup, press the shutter button all the way down to take the shot.You should get a shot which looks like this:
    You can see that the cup is in focus and the background is blurred.

    You achieved this shot using the aperture.

    And now is the time to explain why we followed the additional three steps we took.

    The first step was that you had to make sure the background was slightly far away from the cup. This is because the farther away the background is, the more blurred it will be because the more out of the area of focus it will be.

    The second step was to make sure you are shooting in line with the cup. The reason I asked you to do this is so that you avoid shooting from an up to down angle. When you shoot from an up to down angle, most of the background becomes the surface of the table on which the cup is kept. Since this surface is very close to the cup, it comes within the area of focus, and hence seems sharp. The moment you move your camera in line with the cup, the background becomes something which is far away from the cup.

    Hence these first two steps were carried out to achieve one objective – to make sure the background is far away from the cup so it gets blurred more.

    So remember whenever you are trying to shoot anything in which you want to blur the background, it always helps if the background is far away from the subject.

    The third step we took was to make sure we moved in close to the cup so the cup appeared big enough in the frame. We did this either by going physically close or zooming in.

    The reason we do that is because the closer you are to the subject, the more blurred the background will be. That’s why whenever you are trying to blur the background, it’s advisable to fill the frame with the subject. For example, if you’re shooing a person, make sure they are appearing big enough in the frame. If they appear very small in the frame, it means you haven’t got close enough to them and the resulting background won’t be too blurred. So zoom in and get them big in the frame and then shoot.

    So if we have to summarize, there are three important things to remember when it comes to achieving a shallow depth of field to get a blurred background:

    • Make sure the f-stop number is the minimum.
    • Make sure the background is far away
    • Make sure you are as close to the subject as possible

    Once you have accomplished these three things, you are bound to get a great shot.

    Now let’s look at some images that make the use of aperture to blur the background. Make sure you go through the commentary presented under each image:

In almost all portraits shots, we use a small f-stop number to blur the background so the subject stands out. Here I’ve used f2.8. I’m using the 70-200 f2.8 lens which is one of the best lenses to shoot portraits. See the Recommended Equipments and Accessories section at the end of this book in case you wish to buy this lens. While taking this shot, I also made sure we chose a spot where the background was far away from her to blur it even more.

Here, you can see that the bird is in focus and the trees behind have been blurred so as to make the bird isolated and reduce the distractions. When shooting birds, always be on the look-out for instances where the birds are slightly away from the background. Then use the minimum f-stop number your lens allows and take the shot. In this shot, I have used f6.3. I’m using the Tamron 150-600 f/5-6.3 les here. Since I’m zooming in all the way to 600mm, the minimum most f-stop number possible was f6.3, just like when you zoom in on your kit lens to 55mm, the minimum f-stop number is f5.6.

In wildlife photography, majority of the shots make use of a shallow depth of field to blur the background and keep the subject sharp, like in this shot of the monkey on a branch. Again at f6.3.

In this shot, if I had not used a small f-stop number to blur the background, the goats behind would come out sharp and thus take away the viewer’s focus from the crying baby’s face, which is the main subject of the shot. This is at f2.8.

In this black and white shot, I’ve used f5.6 to blur the background.

In this shot, I’ve used f2.8 to blur the flower behind so the emphasis is only on the reflection in the droplet.

This shot brings in a new element. This time, not only is the background blurred, but the foreground is blurred to. I have purposely kept the camera on the ground so blades of grass come in front of it. Because I am using a small f-stop number and locking focus on the model’s face, the area of focus develops around the model. Anything out of this area will come blurred. The bushes behind and the blades of grass in front are both out of the area of focus. Hence, both are blurred. This is at f2.8.

In this shot, I’ve focused on the drop to make sure it’s the sharpest. Just like the picture we saw before this one, you can see that both the foreground (the sand in front) and the background are blurred. That means I’m using a small f-stop number (f2.8 in this case). You can see that the only part of the sand which is in focus is that which is directly underneath the drop. This is because when I focus on the drop, the depth of field or the area of focus develops around the drop. Hence those things that are very close to it are the only ones that come out sharp.

Here you can see that the things around and near the squirrel are sharp but the background behind is blurred. This is shot at f6.3.

You must have seen shots like these during the Diwali festival. Now you know what’s happening here. Those nice little spheres you see in the background are nothing but small lights that have been blurred using a small f-stop number. Simple, isn’t it? I’ve used the kit lens here and this is at f5.6.

Food photography involves the usage of a shallow depth of field all the time because in majority of the food shots, you have to blur whatever is in the background. But let’s suppose I wanted the mug of beer to be sharp too. Then what would I do? I would just increase the f-stop number to make the area of focus larger.

In food photography, it’s a usual practice to place the ingredients behind the main food item and blur them slightly. For instance, when shooting this mango cake, I’ve placed the mangoes behind it and used the smallest f-stop number to blur them. But the problem here, like in most food shots, is that the ingredients are very close to the food item. So there is a good chance that they can come within the area of focus even at smaller f-stops. Hence, for food photography, it’s a must that you use a lens that allows your f-stop number to go very low so you can decrease the area of focus considerably. Now your kit lens allows you to go down only till f3.5. This may not be enough. So a better option would be to use a lens like the 50mm f1.8. This lens will allow you to go to f1.8, thereby enabling you to blur something that is very close to the subject too. In the shot above, I’ve used an f-stop of f2.8. See the Recommended Equipments and Accessories section if you wish to purchase the 50mm f1.8 lens.

When shooting events, one of the techniques used by photographers to add depth to a shot is to deliberately shoot through obstacles. Here, I’ve gone behind the crowd to shoot through the space between their heads, so as to give a feeling that you are actually seeing this scene from the back. But it’s important that I’m using a small f-stop number to blur those heads. I’ve used f2.8 here.

You don’t always have to blur backgrounds to isolate the subject. Sometimes, it can be used for art too. For instance, while doing a shoot for this 1 year old, I’ve used a small f-stop number to throw his mother’s face into a blur. The contrasting sharpness between their faces makes this shot artistically better. If both the faces were equally sharp, it would not have looked that good aesthetically. This is at f5.6.

Another shot where blurring the background has resulted in a more artistic shot. If the monk behind was sharp, the shot would lose its appeal. This is at f3.5.

As you know by now, the part where you lock the focus on comes sharp and if you use a small f-stop number, the areas ahead and behind that shot come out blurred. So in this shot, I have locked focus on this woman’s left hand. The parts behind and ahead of it come out blurred as I’m shooting this on f2.8

Exercise for Deeper Depth of Field (Keeping everything in focus)

Till now, we’ve been using a shallow depth of field to blur things in the background or the foreground.

But aperture is also used to keep everything in focus in a shot.

Let’s repeat the exercise we just did for blurring the background.

But this time, there will be one difference. Instead of a small f-stop number, we will use a large f-stop number because we want the background to come sharp.

So make the following changes:

  • Use a large f-stop number like f22
  • Use a shutter speed of 1/40
  • Increase ISO to 6400 (the reason for doing this will become clear when you learn about ISO later on in the book)

Now, make sure that you are in a very well-lit room. Then follow everything like last time around and take the shot. You’ll get an image like the one below:

You can see that this time the background is in focus. This is because we used a larger f-stop number.

So anytime you have a shot where you want most of the scene in focus, you use a larger f-stop number.

This is typically done for landscape shots like below:

In all the shots above, it’s important that everything comes in focus. So for landscape shots, we use a higher f-stop number like f11, f13, f16, f22, etc.

For example, look at the shot below:

Here, if I use a small f-stop number and focus on the Buddha idol, the background will come out blurred. But since I want the whole scene in focus, I have to use a higher f-stop number. I have used f16 here.

Terminology Associated With Aperture

Here’s some terms that are frequently used in when it comes to talking about stuff related to aperture:

Bokeh: Bokeh refers to the blurred background we have been talking about. For instance, shots like the Diwali diya one that you saw before where the lights behind were blurred, are referred to as bokeh effect shots.

Shooting wide open: Shooting wide open refers to using a smallest f-stop number. Why? Because at smaller f-stop numbers, the aperture hole is open wide.

Depth of field: As we already learned before, this refers to the area that is in focus in a shot.

A fast lens: A fast lens refers to a lens which allows you to use a very low f-stop number, like f2.8, f1.8, f1.4. The reason they are called fast lenses is because they allow you to use higher shutter speeds. You don’t have to understand what that means right now. Once, you learn about shutter speed and exposure meter in the next few chapters, you’ll be able to understand this.

 Next Chapter: Shutter Speed