back to top

What is Exposure in Photography? (And Why it Matters)

Last updated: September 21, 2023 - 17 min read
ExpertPhotography is supported by readers. Product links on ExpertPhotography are referral links. If you use one of these and buy something, we make a little money. Need more info? See how it all works here.
Subscribe Below to Download the Article Immediately

You can also select your interests for free access to our premium training:

Your privacy is safe! We will never share your information.

Knowing how to control light allows you to create different artistic results. That’s why you must learn how to use exposure to grow as a photographer.

Before you continue reading this article, please grab your camera. We’ll use it to see how exposure works in real life.

eBooks and Courses for Everyone

What is Exposure in Photography

In simplest terms, exposure refers to the amount of light that your camera sensor records.

Sounds easy enough to understand, right? So why is exposure significant in photography?

Manipulating the exposure with your camera is a skillset that you need to master. You see, it’s not enough that you know all the knobs and buttons you need to adjust. It’s also just as crucial to understand why and how you’re making those adjustments.

What Is the Exposure Triangle?

This is perhaps one of the most important terms you need to learn when it comes to photography. It’s called the exposure triangle because it involves three elements that work together to control light.

So what are the three components of exposure in photography?

ISO, shutter speed, and aperture are responsible for controlling the amount of light entering your camera. Each works differently from another. But they all work together to achieve correct exposure.

Let’s discuss each component of the exposure triangle to give you a better how each one influences exposure.


You probably read this term a lot in photography tutorials. But what is the camera ISO, exactly? You can think of it as your camera’s sensitivity range to light.

Most ISO in-camera ranges from 100 to about 12,000 these days. However, high-end cameras can reach up to 30,000 or even more. Some also feature extended ISO, which uses a digital process to boost values up to 100,000 or more.

When it comes to exposure, ISO 100 is often the lowest sensitivity value. That means you can only use it in daylight. In darker conditions, you’ll need a higher number to create a proper exposure. For instance, you have better chances of taking pictures at night with ISO 800 than ISO 100.

The problem is that using such high exposure values creates a lot of image noise. So expect your image to look grainy as you step up from 100 to 800 or more.

Every camera sensor also has a threshold when it comes to image noise. For older cameras, you’re most likely going to end up with distracting grainy photos if you go beyond 800 or 1,000 (even if your native camera ISO is 12,000). But for modern cameras, you can use 3,200 or even more with minimal noise.

When it’s dark out, don’t crank up your ISO on camera too high. Do some test shots and figure out how high you can get before you end up with distracting noise. Otherwise, just stick to lower values to maintain the quality of your photos. When possible, stick to 100 or 200 for daylight exposure.

For dim conditions, you can go as high as you can before image noise becomes overwhelming. In most modern cameras, that threshold is between 3,200 to 6,000. Although we recommend you only use these values for night photography.

Long exposure night photography with traffic lights in the road

Shutter Speed

Now let’s go to the next crucial element in exposure photography: Shutter speed.

Just like ISO, shutter speed also controls the amount of light that gets into the camera.

So what makes shutter speed different? Unlike ISO, which deals with the camera’s light sensitivity, shutter speed is responsible for how long the light hits the sensor.

You see, your camera needs a certain amount of light to achieve correct exposure. When there’s plenty of daylight, your shutter only needs to stay open for a short time. But when it’s dark, it needs to remain open longer so that it can gather enough light.

With shutter speed, you can time how long you want the shutter to open to achieve correct exposure.

The fastest shutter speed is about 1/8000th of a second for most cameras. The slowest is 30 seconds—the slower the value, the more light it lets in.

Fast shutter speeds such as 1/8000th of a second are perfect for daytime use. Why? Because the shutter doesn’t have to stay open for a long time to gather the right amount of light.

But 1/8000th isn’t suitable for low light situations. Mainly because it doesn’t let the shutter stay open long enough to achieve correct exposure, so when it’s dark, it’s always best to use slow shutter speeds, instead.

As we mentioned before, the slower the shutter speed, the more light gets in. So if you’re shooting indoors with artificial lights at night, 1/15th of a second may be enough. But if you’re photographing stars at night, then 10 to 30 seconds may be necessary.

Long exposure night photography of a traveller at the night

Bulb Mode

Explaining shutter speed in photography isn’t enough if we don’t mention Bulb Mode. This feature allows you to keep your shutter open for however long you like as long as your finger is on the button.

Now, why is Bulb Mode crucial? You see, the slowest shutter speed for most cameras is 30 seconds. In most situations, it’s enough to create a proper exposure, especially in low-light conditions.

But there are times when you need to keep the shutter stay open for longer. And that’s when this feature comes in handy. It allows your camera to record enough light in conditions with extremely low light so you can produce a proper exposure.

When using Bulb Mode, you may need to guesstimate how long you need to keep the shutter open. But if you want a be more precise with your exposure, you can also try the 500 Rule in photography.

Bulb Mode is perfect for all sorts of night photography. You can use it for anything from astrophotography to nightscapes.

The only issue with Bulb Mode is that it causes a lot of motion blur. Since it keeps the shutter open for longer than 30 seconds, all the movement it records becomes hazy. Even touching the camera prevents you from recording sharp images.

When you’re using Bulb Mode for your photography, we recommend that you set your camera on a tripod. It would also help a lot to use a remote to prevent camera shake. That way, you end up with great exposure.


In photography, aperture refers to the opening in the lens that lets the light into the camera.

When not in use, the aperture remains closed. But once you press your camera’s shutter button, it stays open for a few moments and closes once it completes an exposure.

In many point-and-shoot cameras, the aperture size is the same. In other words, the area of the opening doesn’t change at all.

But in most modern cameras, the size of the aperture changes depending on the amount of light available. When it’s bright outside, it usually stays small. But when it gets dark, you can make it wider so that it can gather more light.

So how does an aperture change its size? The answer lies in a mechanical contraption called the diaphragm. It’s made up of several blades that slide together to adjust the opening.

In photography, the aperture size is measured in f-stops. The narrowest aperture size is either f/32 or f/22, and the widest is often between f/1.8 and f/1.2.

What Does F-Stop Mean in Photography?

Do you still feel like you need to know more about the F-stop? In simple terms, it’s a value system that measures the amount of light coming into the camera.

The F-stop is often used when adjusting the aperture size. We already mentioned that the aperture could go as wide as f/1.2 and as narrow as f/32. But what do all these numbers mean in photography?

Why is f/1.2 the widest setting and f/32 the narrowest?

It will help a lot if you think of F-stops in terms of fractions. If you switch f/1.8 to 1/1.8, then it starts making more sense.

When it comes to fractions, you learn that 1/2 is more significant than 1/4. So if you use f/2, that just means you’re letting in more light than if you were using f/4.

The same principle applies to the other f-numbers. f/32 or 1/32 lets the least amount of light in because it’s smaller in value as compared to f/4 or 1/4.

f/32 is best for bright situations since it’s a small opening. Meanwhile, f/1.2 is perfect for dim conditions since its wide opening lets in a lot of light.

How Does the Exposure Triangle Influence Exposure?

The reason why ISO, shutter speed, and aperture are collectively called the Exposure Triangle is that they’re all interconnected. When you change the ISO, you’ll affect the shutter speed and aperture as well.

To better understand how the exposure triangle influences exposure, you’ll need to turn on your camera.

First, set your camera to ISO 100. Then switch your Mode to Aperture Priority. Choose f/3.5 and point your lens to a constant light source such as a light bulb. Now take note of the shutter speed on your display.

Without moving your camera, change your ISO to 200. Since you’re on Aperture Priority, the aperture size will stay the same at f/3.5. But now look at your shutter speed. Did you see it change?

Your shutter speed is probably faster now than when the ISO was still 100. Why? Because you just brightened the scene by adjusting light sensitivity. So the shutter doesn’t have to stay open for too long to create an exposure.

If you set your ISO to automatic, you’ll see how both the shutter and ISO values fluctuate as you change the aperture.

So what’s the reason behind the interdependency between these components? You need to remember that all of them can control the amount of light coming into the camera. If one element changes, all the others have to adjust as well, so the camera still achieves a correct exposure. Otherwise, your images will end up looking dark or overexposed.

Women adjusting camera exposure settings.

How Do You Use the Exposure Triangle to Achieve Correct Exposure?

There are several ways to adjust the ISO, shutter speed, and aperture. Each of the methods we’ll be discussing allows you to achieve proper exposure. But each option also affects the way your photo looks. So it’s essential that you know which component you change to get the result you want.

Use Aperture Priority for the Correct Exposure

We mentioned Aperture Priority earlier. But how exactly does it work, and how do you use it?

Aperture Priority allows you to keep the aperture size constant while taking pictures. To compensate, the camera automatically changes the ISO and the shutter speed to achieve proper exposure.

So when is Aperture Priority useful? You’ll need it for low-light situations and when you want it to control your depth of field.

Let me explain:

When you don’t have enough light, you’ll need to use the widest aperture possible to create a proper exposure. You need to switch to Aperture Priority to make sure the lens opening stays wide open as you take photos.

But changing the aperture size affects the sharpness of your image. The term for this phenomenon is the depth of field. If you want a blurry background, you’ll need to use a wide aperture, such as f/1.2 or f/1.8. If you want everything to look sharp, then f/16 or f/22 would be ideal.

With that in mind, what should you do if you’re taking photos in daylight but still want a blurry background? The beauty of Aperture Priority is that it will let you use f/1.8 to create a shallow depth of field. To compensate for all that light coming in, your camera increases the shutter speed and lowers the ISO automatically to achieve correct exposure.

Use Shutter Speed Priority for Low Light Situations

The shutter speed priority works much like the Aperture Priority. But the only difference is that this time, the shutter speed value stays constant. The camera automatically changes the aperture and ISO to create a proper exposure.

When is shutter speed priority useful? If there’s barely any light available, it’s not enough to use a wide shutter to create a decent exposure. That’s when you can use slow shutter speed to allow you to gather more light.

However, you need to beware that long exposure can cause moving objects to look blurry in photos. Why? Because if a shutter stays open for two seconds or longer, any moving element may not be in the same position anymore. As a result, you’ll end up with double images or even ghosting.

In contrast, if you use a fast shutter speed such as 1/125th of a second, you’ll end up with sharp images. Why? Because the shutter opens and closes so fast that it freezes the motion of the moving element.

The caveat is that you can only use fast shutter speed when there’s enough amount of light. If you find yourself in dim conditions, it’s best to stick to slow shutter speed.

Set the ISO for a Clean Exposure

Now ISO is a little tricky because, in some ways, it’s separate from Aperture and Shutter Speed.

You have the option to set a fixed ISO on your camera or choose Auto Mode.

If you’re a beginner, Auto Mode is best to use because it lets the camera set the exposure for you. But as we mentioned before, high ISO also produces a lot of noise in low-light conditions. So if you’re shooting at night, you have no control over the graininess of your images.

For a clean exposure, use Manual and select a low ISO. In the daytime, ISO 100 is perfect. But if you find yourself in dim conditions, feel free to go between 800 to 3,200. Just remember that as you go up, the amount of grain in your image also increases.

You can also set your ISO to auto but set a maximum value. That way you know your camera won’t choose ISO 12,000 and produce a super grainy exposure.

Whatever ISO value you set will determine the shutter speed and the aperture values to achieve a proper exposure.

For instance, a high ISO in Aperture Priority Mode will yield a faster shutter speed. Conversely, a low ISO will result in slower shutter speed.

The same concept applies even when you use Shutter Speed Priority. A high ISO will result in a smaller aperture, and a low ISO will result in a wider aperture.

And how about if the ISO is automatic? If you choose Aperture Priority, then the aperture size stays constant while the ISO and shutter speed change.

Conversely, if you choose Shutter Speed Priority, the shutter speed stays constant while the ISO and aperture change.

Picture of DSLR camera placed on tripod.

How Do You Adjust Exposure in Manual Mode?

Manual Mode is quite challenging for beginners in photography because they would have to know which settings to use. And it’s especially challenging to know that setting up one component means changing the others too. Otherwise, the exposure will not be correct.

If Manual Mode in photography is complicated, then why use it? The simple answer is that auto modes, including Aperture and Shutter Speed Priority, don’t always achieve the correct exposure.

Manual Mode allows you to change the ISO, shutter speed, and Aperture manually to get the best exposure.

So how do you use Manual Mode? We’ll show you how easy it is with this trick:

You can start by switching to either Aperture Priority or Shutter Speed Priority.

For the sake of demonstration, let’s choose Aperture Priority and select f/2.8 as the aperture size.

Point the camera to the scene you want to photograph and take note of the shutter speed and the ISO.

Now switch to Manual Mode and set your shutter speed and ISO to match the exposure settings in Aperture Priority.

Once you have all the settings, decide whether you want to move the ISO and shutter speed or down.

If your exposure looks dark, then you may want to bump up your ISO or lower your shutter speed.

And if your exposure looks blown out, then you may want to lower your ISO or use faster shutter speed.

To make it easy for you, adjust your settings in one-stop increments. In other words, don’t go from ISO 100 to ISO 800 right away. Go to ISO 200 first and see if there’s any improvement in the exposure. If not, keep going up one stop at a time until you get the exposure you desire.

If you want to save time, keep your ISO constant and just move the shutter speed instead. That way, you don’t have to focus on two things at once to get the exposure you want.

See how easy it is to achieve the correct exposure using Manual Mode in photography?

What Is Exposure Compensation in Photography?

You don’t always have to use Manual Mode if you want to override your camera’s automatic exposure settings.

All you have to do is turn on your exposure compensation to override your camera’s settings.

Let’s say you’re using Aperture Priority, and you’re not entirely satisfied with the exposure. What do you do? Simply press Exposure Compensation and move up to increase the exposure or move down to decrease it.

Once you set your new exposure setting, all you have to do is take a picture, and you’ll get the exposure you desire.

Exposure compensation is perfect for taking photos with lots of black or white areas.

Why? Because your camera doesn’t see black and white as humans do. Instead, it sees shades of grey. So when you see a scene with lots of white (like snow), it would be best to turn your exposure compensation up. That way, the snow would look white and not grey.

The same goes when it comes with scenes filled with lots of black. But instead of turning up your exposure compensation, you turn it down. As a result, you can be confident your black wouldn’t look greyish.

How Can You Master Exposure in Photography?

Technically, the exposure triangle is a mathematical equation. The settings you use have predictable results. If you change your shutter speed one notch, then it only makes sense that the aperture should also move one notch.

Just remember that if you increase one exposure setting, you have to decrease the other or vice versa. What do I mean by this? Let’s say your aperture setting is f/2.8, and your shutter speed is 1/100th of a second. If you widen your aperture to f/2, you’ll need to increase your shutter speed to 1/125th.

So why increase the exposure setting to 1/125th instead of decreasing it to 1/60th? The main reason is that you’re letting more light in when you changed your aperture from f/2.8 to f/2. To avoid overexposing your photo, you’ll need to increase the shutter speed to make up for that extra light coming in. That way, you can still correctly expose your image even after you make your adjustments.

Magnificent long exposure landscape photography of sea sunset.


There’s nothing wrong with taking advantage of Aperture and Shutter Speed Priority instead of Manual Mode.

But even when you use auto settings, it’s essential that you still know how the exposure in photography works. That way, it would be easy for you to troubleshoot problems you encounter while taking pictures. Your camera doesn’t always get it right despite all the features it offers.

When the situation demands you to use Manual Mode, then at least you can be confident you’ll get the shot using the exposure triangle.

Don’t miss out on our Infinite Exposures course to learn how to take perfect long exposure shots! 

eBooks and Courses for Everyone