The Exposure Triangle: The Fundamental Elements of Exposure

The Exposure Triangle: aperture, shutter speed and ISO

When I started in the photography world, words like Aperture, Shutter Speed and ISO were foreign to me, and it took me a couple of weeks to take pictures in full manual mode after read a photography book and look in Internet to obtain more information. You might be feeling a little confused, and you may even feel like you will never get your camera out of Auto mode, because it’s just too hard to understand. But I’m sure after read this post you will start to try by yourself in manual mode and experiment the different possibilities.

What is Exposure in Photography?

In the simplest of terms, exposure for photographers refers to how an image is recorded by camera sensor and how much light is captured. Basically, it determines what the image you capture will look like.

Understanding the Exposure Triangle

ISO, Aperture and Shutter are known as the “exposure triangle”. If you know how to control or adjust these elements on your camera, taking well exposed photos will not be a problem for you. Take your time to know your camera and find each adjustment. The most important thing before all, it’s to know your controls and how to change them to have a correct exposure.



With the experience, you will be able to make the correct adjustment faster and faster. Finally, it has to be by intuition, as a athlete in any sport.

The three elements are:

  1. ISO – the measure of a digital camera sensor’s sensitivity to light

  2. Aperture – the size of the opening in the lens when a picture is taken

  3. Shutter Speed – the amount of time that the shutter is open

It is at the intersection of these three elements that an image’s exposure is worked out.

Most importantly – a change in one of the elements will impact the others. This means that you can never really isolate just one of the elements alone but always need to have the others in the back of your mind.

Side 1: Aperture

Aperture. Aperture controls the brightness of the image that passes through the lens and falls on the image sensor. It is expressed as an f-number (written as “f/” followed by a number), such as f/1.4, f/2, f/2.8, /f4, f/5.6, f/8, f/11, f/16, f/22, or f/32.

A wider aperture (or lower f-number) means more light will be let in by the lens, simply because the opening is larger. A narrower aperture (or higher f-number) allows less light to reach the sensor.

  • SMALL numbers (like f/1.8) = wide open aperture (large opening).

  • BIG numbers (like f/22) = small aperture (teeny opening).

Another thing that can be affected by aperture is depth of field, or how much of your picture is in sharp focus. A wide open aperture (small number) will make less in focus, and a closed down aperture (big number) will make more in focus.



Try to use Aperture Mode in your camera to see the difference between wide and small apertures.

Side 2: Shutter Speed

In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph. The amount of light that reaches the film or image sensor is proportional to the exposure time. 1⁄500 of a second will let half as much light in as 1⁄250.

If you have a wide open aperture, your shutter speed will need to be faster, because you’re already letting a lot of light in the lens opening. If your aperture is small, your shutter will need to move slower, so there is more time for light to get to the sensor.

If you want to freeze the action, or hand-hold your camera, then a faster shutter speed is needed. If you want to create blur, then you need a slower shutter speed. 



You can try your Shutter Priority Mode to obtain different results. Long exposure is amazing when you take pictures by night but remember to use a tripod to have more stabilized shots. As you play with these different priority modes, notice what the camera chooses for the rest of your settings. The more you pay attention to these things, the more knowledge you’ll have to be able to set everything yourself in the future.

Side 3: ISO

ISO measures the sensitivity of the image sensor. The same principles apply as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain. ...



By choosing a higher ISO you can use a faster shutter speed to freeze the movement. But take care about this, higher ISO means higher grain on your pictures.



In low light conditions, you should increase your ISO to obtain a correct exposure.

Side 4: EVs and Stops

Almost all digital cameras have an Exposure Value (EV) Compensation setting. This setting is needed because the camera can sometimes make incorrect assumptions about the lighting of a photo. Changing the EV will make sure your photos are always correctly exposed.

In photography, a "stop" is a widely misunderstood concept, feared by many because it sounds so complicated. However, it's actually very simple:

A stop is a doubling or halving of the amount of light let in when taking a photo.

For example, if you hear a photographer say he's going to increase his exposure by 1 stop, he simply means he's going to capture twice as much light as on the previous shot to obtain the correct EV.

This amount of light captured while taking a photo is known as the exposure value as said previously, and it's affected by the exposure triangle - the shutter speed, the aperture diameter, and the ISO. These are all measured using different units, so the concept of "stops" was invented as a convenient way to compare them.

Forward, perhaps I will repeat some concepts but if you understand what they are the stops and how the 3 variables can affects your pictures, you will understand the exposure triangle and how to use it at any moment.


Shutter speed measures how long your camera's shutter is left open during a shot. The longer it's open, the more light it lets in, and the greater your total exposure will be. Doubling or halving your shutter speed produces an increase or decrease of 1 stop of exposure.

Common shutter speed stops.

Common shutter speed stops.

For example, changing from 1/100 of a second to 1/200 lets in half as much light, so we can say we've decreased the exposure by 1 stop. Similarly, going from 1/60 to 1/30 lets in twice as much light, giving a 1 stop increase in exposure.

Most cameras allow you to adjust shutter speeds in increments of 1/3 of a stop, so 3 turns of the dial either way will adjust your exposure by 1 stop.


ISO speed describes how sensitive your camera's sensor is to the light that hits it. A more sensitive sensor will produce the same overall exposure from less light, meaning that you can use a narrower aperture or faster shutter speed in the same conditions.

Common ISO speed stops.

Common ISO speed stops.

ISO is measured using values that correspond to the ASA scale for film, with a higher ISO number relating to a more sensitive sensor. As with shutter speed, doubling the ISO number gives an increase of 1 stop, while halving gives it a decrease of 1 stop.

For example, switching from ISO 100 to ISO 200 doubles the sensor's sensitivity, producing a 1 stop increase. Moving from ISO 800 to ISO 400 is a 1 stop decrease. Most cameras let you change ISO speed in increments of 1 stop.


Aperture is measured using the "f-number", sometimes called the "f-stop", which describes the diameter of the aperture. A lower f-number relates to a wider aperture (one that lets in more light), while a higher f-number means a narrower aperture (less light).

Common aperture stops.

Common aperture stops.

Because of the way f-numbers are calculated, a stop doesn't relate to a doubling or halving of the value, but to a multiplying or dividing by 1.41 (the square root of 2). For example, going from f/2.8 to f/4 is a decrease of 1 stop because 4 = 2.8 * 1.41. Changing from f/16 to f/11 is an increase of 1 stop because 11 = 16 / 1.41.

As with shutter speed, most cameras let you control your aperture in 1/3 stop increments.


The great thing about stops is that they give us a way to directly compare shutter speed, aperture diameter, and ISO speed. This means that we can easily swap these three components about while keeping the overall exposure the same.

Let's say you're shooting a scene using a shutter speed of 1/60 of a second, an aperture of f/8, and an ISO of 200. You find that while the scene is well exposed, your subject is turning out a bit blurry, so you decide to increase the shutter speed to 1/120 of a second.

This change of 1 stop will result in the next photo coming out dark, because you're now letting in half the total light as before. In order to correct this, you need to reclaim that 1 stop reduction from somewhere else. Now that we have a way of comparing settings, this is simple.

You could open the aperture wider to let in more light - moving from f/8 to f/5.6 is an increase of 1 stop, so we've got back to our original exposure. Alternatively you could double the ISO speed from 200 to 400, again resulting in a 1 stop increase.

As you can see, stops are a really easy way of adjusting our camera's settings while making sure we don't ruin the photo's overall exposure.


When adjusting the three components of exposure you should be aware that each one affects your photos in other ways, which may not always be desirable:

Shutter speed - If your shutter speed is too slow your photo may blur, either from movement of the camera or movement of the subject.

Aperture - A wide aperture produces a narrow depth of field, so if you make it too wide you may have trouble keeping everything in focus. On the other hand, a narrow depth of field can help to isolate the subject, and is often something that you want; if so, you need to avoid using a narrow aperture.

ISO speed - The more you increase your camera's ISO, the more digital noise your photos will exhibit. This can make your image look grainy and reduce its sharpness.

As with everything in photography, adjusting these three settings is a balancing act. You need to decide what effects you want in your shot and choose settings that will produce them while minimising the potential downsides. Exposure stops are a really useful tool for doing this, helping you swap settings around with ease and giving you more control over your scene.

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Rule of Thirds: start taking superb photographies

Rule of Thirds: Composition Photography

The rule of thirds is an essential photography technique. It can be applied to any subject to improve the composition and balance your images.

This technique is a basic rule for artists, not only for photographers. This Rule of Thirds is perhaps the most well-known ‘rule’ of photographic composition.

It's an important concept to learn as it can be used in all types of photography to produce images which are more engaging and better balanced. If you take an introduction to photography class, more than likely, one of the very first things you will learn is the “Rule of Thirds”. Even if you haven’t taken a photography class, you have still probably heard this term.

What is the Rule of Thirds?

The rule of thirds involves mentally dividing up your image using 2 horizontal lines and 2 vertical lines, as shown below. You then position the important elements in your scene along those lines, or at the points where they meet.

Rule of thirds

Rule of thirds

As you’re taking an image you would have done this in your mind through your viewfinder or in the LCD display that you use to frame your shot.

With this grid in mind the ‘rule of thirds’ now identifies four important parts of the image that you should consider placing points of interest in as you frame your image.

Not only this – but it also gives you four ‘lines’ that are also useful positions for elements in your photo.

When taking your photo, you will want to ask yourself:

  • What are the most important elements of my photo?

  • Where should I should I place them within my photo?

Realize that your subject doesn't have to be exactly on the hot-spot, just near to it. You may have to movearound when shooting to make this happen and get best composition.

The Rule of Thirds states that a photograph has the greatest impact and ability to capture a viewer’s attention when your image subject and important foreground and background elements are placed in the composition near the junction of these lines. Horizons are best placed along one of the two horizontal lines, rather than in the center of a photo. Vertically oriented subjects, like people standing, are best placed along one of the vertical lines, with the person’s back closest to the edge of the photo, leaving room ahead of them in the direction they’re facing.

Rule of Thirds in Landscape Photography

New landscape photographers often mistakenly place the horizon right in the middle of the photo.  This tends to give the feeling of the image being split in two - which is not generally pleasing to the eye.

Knowing the rule of thirds is very helpful here, as placing the horizon on one of the horizontal lines will naturally balance the image and allow you to highlight the area of the photo that you want.

For example, you should place the horizon on the bottom line if you’re trying to highlight a beautiful sky or sunset. Alternatively, if want the focus to be on the land, you would place the horizon on the top line.

Rule of Thirds and Directional Movement

When you’re photographing a moving subject pay particular attention to the direction they are traveling.  You will want to place them near the hot spot or line on the opposite side from where they are going.

For example, if your subject is a jogger who is running from right to left, make sure place them on the right vertical line or hotspot.  This will give the appearance your subject moving forward and also show where they are headed.

Rule of Thirds and Where Your Subject is Looking

If your subject is looking in a particular direction, make sure to place them on the opposite side from were they are looking. This will leave empty space ahead of them and prevent the appearance that they are looking off into nothingness.

For example, if your subject is looking to the left, place them on the right vertical line.  This will provide more natural balance and allow the viewer to understand what they are looking at.

If you find that there are no determining factors on which side is better for placement, choose the right.  Because we read from left to right, our eyes will naturally focus more strongly on the right side.


The Rule of Thirds is not an infallible law, but it is a good point of reference to keep in mind, just as artists have done for hundreds of years. Excellent photos can certainly be taken with your subject or horizon centered in the middle of the frame, but generally you’ll find that the Rule of Thirds really does improve the composition and balance of a photograph.

However, learn to use the rule of thirds effectively before you try to break it - that way you can be sure you're doing so in order to get a better composition, rather than just for the sake of it.

A few examples of when breaking the rule of thirds can make for a better photograph include:

  1. Highlighting the symmetry of a subject or location by centering the photo.

  2. Making a subject appear larger and more intimidating by placing them in the center of the photo.

  3. If you want to draw the eyes inward - perhaps a photo of a narrow pathway that you want your viewer to focus on.

  4. The subject is nicely framed and centering makes for a stronger photo.


You can easily apply the rule of thirds to existing photos by cropping them. This allows you to reposition the important subjects in your image, moving them into more pleasing positions.

If you don’t get your perfect positioning in camera (and who does), you can use Lightroom and Photoshop, they includw a rule of thirds overlay to help guide you.