Understanding Aperture | A Comprehensive Beginner’s Guide

Understanding Aperture | A Comprehensive Beginner’s Guide

Do you know what is the world’s best camera ever? No not Canon, not Nikon, not the Sony A9…..its your eyes. Since you are a beginner now maybe you wouldn’t realize the full meaning of this sentence but I assure you, the more you learn about photography the more you would marvel at the simple, pure amazingness of your humble eyes.

So understanding aperture right? Let’s get on with it.


Very simply aperture means an opening, hole or gap. In our world of photography it is the small little opening at the back of the lens through which the light comes into the camera.

Where is it actually?

The aperture is located at the back of every lens. Ideally the aperture lies in the region where the lens meets the camera.

camera cutmodel cross section

Why do we care?

We care so much because the aperture governs two EXTREMELY important aspects of photography:

  1. The amount of light entering the camera.
  2. The depth of field (don’t worry I will explain).

How does the aperture control the amount of light or the depth of field?

It is very simple actually. The aperture changes in size to regulate the amount of light that enters the camera and the depth of field.

When we have a larger aperture (larger hole), a lot of light enters the camera and similarly when the aperture is small, little amount of light enters the camera. Try and keep this in mind. I will explain the depth of field later in this article but it is important that you understand this basic concept of larger and smaller aperture.

How is the size of the aperture controlled?

Every lens has some blades at the back which expand or contract to make the aperture smaller or larger respectively. It look something like this.


How do we control it on our camera?

We control the size of the aperture by selecting the specific aperture value on our camera. Like dress and shoe sizes the aperture also has various sizes which are used for various purposes. The sizes of aperture looks something like this:

aperture value pattern

Now this might seem confusing and odd but this is how aperture values are written. (Why…. do you ask? Since aperture value is actually a ratio of the focal length of the lens and the diameter of the entrance pupil. Do not worry you do not need to understand anything of this now. You time will come.)

Unfortunately though you have to remember these numbers to understand exposure values and the exposure triangle later on. Do not panic so much I have an easy way out of this. Look at the numbers above. There is a very easy pattern there, do you see it?….No? Let me show you.

Except for the first two numbers (1.4 and 2) all the other numbers are exactly double of the number two places before it. Here it is:

aperture value pattern

Just remember 1.4 and 2 and then keep on doubling the numbers to get your next aperture value. Easy right?


What do these numbers mean?

These numbers are what in photography called ‘f-stops’. F-stops are very important in understanding aperture and photography in general. Remember when I said earlier that we care about the aperture because it governs two very important aspects of photography:

  1. Amount of light entering the camera.
  2. Depth of field.

Well, this is how it does it. Let me break up the consequence of changing the aperture from say 2 to 2.8.

Change in amount of light: When you increase the aperture value from 2 to 2.8 what happens is the blades of the lens expands out and the opening/hole becomes smaller. As the opening becomes smaller it lets in less light. If you increase the aperture value even more say f/11, the opening becomes even smaller and lets in even less amount of light.

Change in depth of field: Depth of field is defined as the amount of the picture that is sharp. For example:

This is an image with a deep depth of field (notice how so much of the image is sharp, from the wooden railings in the foreground to the mountains at the back).

landscape of a mountain


This is an image with a shallow depth of field (notice how only the van is sharp, while the background is blurry. Very small part of the image is actually sharp).

shallow depth of field

The depth of field of the image is directly related to the aperture value you use, i.e, higher the aperture value you use, more depth of field you will have and vice versa. So, when you use an aperture value of say f/1.4 (small aperture value) you have very little depth of field to play with; but when you use an aperture value of say f/22 (large aperture value) you have a huge depth of field and nearly everything in that image would be sharp and in focus.

Depending on the subject and the type of image that you want to create you can select any aperture value. It is one of the most interesting creative freedom you have as a photographer.

So when should you use which aperture?

There are no such thing as “rules” in photography. Anyone who says follow this “rule” to get best results is simply misguided. There are NO rules, do not let anyone else tell you any different. You can use ANY aperture for ANY type of photograph that you take. However there are a few preferred aperture values that are used more by some photographers for some specific results.

Landscape: Landscape photographers generally use higher aperture values. You already know by now that a higher aperture values gives us higher depth of field. This means that the photographer can keep everything from the foreground to the background in focus and sharp.

Think about it for a second this does make sense, doesn’t it? Landscape photographers want to make us feel as if we are standing there on that ledge of that mountain and looking at the vast expanse with our own eyes. In order for him to create the same experience for us it is important to use a high aperture value such as f/16 or f/22 to keep everything in the image sharp.

This does NOT mean that you “should” always use a higher aperture value for all your landscapes. There may be a scenario where you want the focus to be on just a single subject in the foreground and do not want all of the image to be sharp. Selecting a smaller aperture value of f/1.4 or f/2.8 is a good idea then to keep the depth of field shallow and hence keep only a certain part of the image in focus.

shallow depth of field

Here in the image as you can see, only the young boys and the grass near them are in focus while the trees in the background are blurry and not sharp. The photographer here used a lower aperture value to create this (lower aperture results in shallow depth of field). The image is even then beautiful wouldn’t you agree?

Portraits: Photographers who shoot portraits generally tend to shoot at comparatively lower aperture values. This gives them a shallower depth of field and hence makes it easy to keep their subjects distinct from the background. Many times the background may be busy, distracting and cannot be changed while shooting a portrait at all. The photographer then may use the shallower depth to make the background completely blurry so that subject remains the main element of the photograph and the eyes of the viewer is drawn towards it and not the background.

Portrait shallow depth of field

Notice how the photographer by using an lower aperture value made sure that he had a shallow depth of field. He then used that little depth of field to keep just the woman in focus and let the background be soft and blurry. This not only draws in the eyes of the viewer towards the subject of the image which is the woman but also makes the image so much better. The background which was originally so busy, is not distracting anymore.

Other genre of photography: This same principal can be applied to ANY genre of photography that you take up. Product, food, close up, photojournalism, glamour, macro, fashion, fine art or aerial  photography they all use the same principle. The bottom line is this; you use aperture to determine the amount of the background you want to include in the final image, as far as depth of field is considered.

  • For including less of the background    -> Lower aperture value, say f/1.4 (which gives you a shallow depth of field).
  • For including more of the background -> Higher aperture value, say f/22 (which gives you a deep depth of field).


A word of caution though:

Before I start discussing this part let me just say that this is a little confusing and may seem a bit difficult at first but I am here with you and I will walk you through it. So, don’t worry, just keep reading and repeat if necessary.

Remember earlier I said that the aperture values are actually ratios of the focal length of the lens and the entrance pupil of the lens? No, you were not supposed to understand it at all. I have kept it for a future discussing when you have already mastered everything we discussed today.

Let me however just tell you this much.

So, because the aperture values are actually ratios the actual size of the aperture has an inverse relationship with the aperture values. It is just this, a higher aperture value represents a smaller aperture and vice-versa. Read the last sentence three time. I am waiting here.


It is just this and nothing else. A smaller aperture value represents a larger actual aperture and vice-versa. So a f/1.4 aperture value actually means a large opening

Large aperture

Similarly a larger aperture value represents a smaller actual aperture. So a f/22 aperture value is actually a very small opening.

larger aperture value smaller aperture

You do not need to know why this is so at this point of time, I will explain why this happens in a later article. Just remember the simple logic.

  • Smaller aperture value -> Larger actual aperture.
  • Larger aperture value   -> Smaller actual aperture.

Diagrammatically it looks something like this (NOT to scale).

aperture value and size


Have you noticed how sometimes photographers use the term “fast lens”? What they mean is that you can use a faster shutter speed with it. Generally photographer use the term “fast lens” while discussing low light scenarios. Since lenses which have a large aperture (hence smaller aperture value) allow more light to come in, most if the time a higher shutter speed could be used with them. In low light scenarios like in music concert or a dark drama theater this can be invaluable, since a larger aperture allows higher shutter speed and that it turn allows you to have shake free, sharp, crisp images.  In case you are wondering a shutter speed of about 1/100 sec or faster is considered fast enough to be used for handheld shooting.

Interesting trivia:

Do you know that you posses actually not one but TWO apertures yourself? You guessed it right they are in your eyes. Look closely at the image below.

Human eye pupil

The pupil acts as the aperture of our eyes. It contracts and expands just like the aperture on our camera lenses to regulate the amount of light that gets in. Have you every felt that the light is too bright when coming out of a dark movie hall? Or when entering a dark room felt that you could see nothing, but then after spending some time you begin to perceive everything in black and white? Well it is just the pupil adjusting itself to give you the “perfect” exposure. To see the phenomenon yourself stand in front of a mirror and try to locate your pupil. Now shine a light (NOT too bright) on your eyes, you will see that the your pupils start to shrink. If you keep looking you will find that once the light is removed, the pupils adjust to the low light again and dilate back to a larger size.

That was all you need to know about aperture and its uses. Understanding aperture is one of the most powerful way to shape your images. Mastering it would help you understand photography in a whole new light and also allow you to make great images. You will soon see for yourself that aperture plays a huge role in the exposure triangle too.

So, go out there and keep shooting amazing.

Best of luck.

Aalok Doot Das

Aalok is a passionate photographer at heart. A night owl and a person who lacks the basic understanding of fashion and clothes. Movie Buff and now in breathless anticipation of the next Christopher Nolan movie.
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