Hi, hello. Let’s talk about exposure and what it means for photography. Exposure is critical when it comes to crafting a good photograph, and it happens to be one of the most difficult things to grasp in photography. How your camera’s sensor is exposed to light determines how bright or dark your image is. Shutter speed, aperture and ISO all play a part in creating an exposure. So, let’s talk about exposure and what it means for your photography.

What is Exposure in Photography

an hdr blended image of a creek in early autumn
A blended image using a bracket of three exposures

For photographers, exposure means how much light reaches the camera’s sensor or film. Since we are in the digital age of photography, we will mostly be using the word sensor.

Here are some key words to keep in mind while you are learning photography:

  • Exposure: the amount of light that hits the camera’s sensor or film. Many photographers will also use the word “exposure” to refer to a single frame or image, especially when shooting brackets or HDR.
  • Sensor: the thingy inside your camera that gathers the light to create an image
  • Exposure Valuation (EV): a number that represents how bright a scene is and determines what aperture and shutter speed are necessary
  • A Stop: the unit we photographers use to refer to doubling or halving the amount of light reaching the camera’s sensor
  • Over-exposed: an image that is too bright because too much light was able to hit the sensor. Many photographers will also use the term blown out.
  • Under-exposed: an image that is too dark because not enough light was able to hit the sensor

Exposure Valuation and Stops

There are a lot of little technical things involved when it comes to photography and especially when dealing with exposure. There is also math, which I am garbage at, so I will try to keep this as not-technical as I can. Please note that there will be links to other sources in the next section. These sources get a lot more technical than I do. The links are here to a) site my sources and b) give you more context if you want it.

What the Heck is Exposure Valuation?

In the film photography days, photographers would carry around a little device called a light meter. These light meters would read the brightness of the scene and then spit out a number. That number would tell you which shutter speeds and apertures would work for that particular level of brightness. That number is called Exposure Value (or valuation) or EV and would legitimately be represented by one number. The light meter would tell you the Exposure Value number and then you would look at a chart to see which shutter speeds and apertures worked for that number (there’s a whole formula you could also use, but math so we’re not going to get into it).

In digital photography we don’t really have to worry about light meters because our cameras do it for us. Unless you go out and get a light meter you will probably never see Exposure Value represented as a single number. However, Exposure Value still comes into play in determining your shutter speed and your aperture. Remember, shutter speed and aperture work together, with the help of ISO to create an exposure.

Further reading:

For more on Exposure Value check out this article (it has graphs and charts)

To learn about light meters check out this article

And to get super technical with Exposure Value check out the Wikipedia

What Are Stops?

an image of a creek showing a correctly exposed frame and an overexposed frame
The same image 2 full stops apart. The brighter image is at 8 seconds, f22, ISO 200. The darker image is at 2 seconds, f22, ISO 200.

In photography, one stop refers to the doubling or halving of the amount of light that reaches the camera’s sensor. Photographers will often say they are “stopping up” or “stopping down” when they are changing their settings to create their exposure. Stopping up means increasing the amount of light that reaches your camera. To do this you would pick a longer shutter speed or a wider aperture. Stopping down means decreasing the amount of light that reaches your camera. To do this, you would pick a shorter shutter speed or a smaller aperture.

Further Reading:

For a super detailed look into Exposure Stops check out this article

The Same Exposure But Different

For each Exposure Valuation there a several combinations of shutter speeds and apertures that will create the same exposure. Yup, you heard that right. There a multiple combinations of shutter speed and aperture that will create an image at the same level of brightness. For instance, let’s say your ISO is at 200 and you don’t change it. You can take a photo at 1/250 shutter speed and f/5.6 aperture and then the same photo at 1/125 shutter speed (stopped up) and f/8 aperture (stopped down) and get the same exposure. Because there are multiple ways to achieve the same exposure, you’re able to choose the shutter speed or aperture you want to capture the scene and adjust (or have the camera adjust) the other setting accordingly.

Creating an Exposure: Shutter Speed, Aperture and ISO

a single exposure of a creek
This image was exposed for 13 seconds at f22, ISO 200

Two things go into creating an exposure: Aperture and Shutter Speed. A third thing, ISO, helps you achieve the aperture and shutter speed you want. Many in the photography world call this the exposure triangle. So, what do each of these things do?

Shutter Speed

Shutter speed determines how long your camera’s sensor is being exposed to light. A faster shutter speed means your the shutter is opening and closing faster, allowing less light to reach the sensor. This means that your image will be darker. A slower shutter speed means that your shutter is staying open longer and allowing more light to reach your sensor. This means that your image will be brighter.

Aperture

Aperture refers to the little hole inside your lens and is denoted with a f followed by a number (f11, f5.6, etc). You can make this hole larger or smaller to allow more or less light in. A larger aperture means more light is able to reach your sensor which means your image will be brighter. A smaller aperture means less light is reaching your sensor which means your image will be darker.

Aperture also affects depth of field which determines how much of your image is in focus. When choosing an aperture keep this in mind and base your aperture on what kind of scene you are shooting and how you want your final image to look.

ISO

ISO is the last thing that helps you achieve the exposure you want. In film photography ISO refers to the sensitivity of the film. In digital photography, the concept is similar though it’s more that your camera is artificially lightening the image when you bump your ISO up. Lower ISOs create darker images and are great for well lit situations like shooting in bright outdoor light. Higher ISOs create brighter images and are great for poorly lit situations like concerts and indoor parties. It’s best to shoot with the lowest ISO possible for the scene you are shooting so that you don’t introduce digital grain.

Putting the Exposure Triangle Together

Putting aperture, shutter speed and ISO together is where things start to get fun and challenging. Remember if you adjust one you may need to adjust the others:

  • A faster shutter speed means you may need a wider aperture and higher ISO
  • A slower shutter speed means you may need a smaller aperture and lower ISO
  • A wider aperture means you may need a faster shutter speed and lower ISO
  • A smaller aperture means you may need a slower shutter speed and higher ISO
  • A lower ISO mean you may need a a slower shutter speed and wider aperture
  • A higher ISO means you may need a faster shutter speed and smaller aperture

All of the images in this article demonstrate this to an extent. For each image in this article I wanted to capture the motion blur in the water. To do this I needed a longer shutter speed. So, my ISO was set pretty low at 200 and my aperture super narrow at f22. This forced my camera to choose longer/slower shutter speeds to get the correct exposures for these photos.

The Over and Under of Exposure

an image of a creek shot at a dark exposure and a light exposure
The same image underexposed by 2 stops on the left and overexposed by 2 stops on the right.

When it comes to exposure, there is really no such thing as the perfect one. Every photographer has a different way of setting up their shots, and creating their exposures, and perceiving the scenes that they are photographing. One photographer might look at a mountain landscape and want to capture the darkness and moodiness of the clouds gathering at the peaks, while another may want a brighter image that capture a happy, sunny day. In this case, the first photographer would under-expose their image, while the second may choose to over-expose theirs.

Under-exposed

An under-exposed image just means that the image is darker than what the correct exposure would have been. Oftentimes when you under-expose an image you will lose details in the blacks and shadows.

When to Under-expose

Intentionally under-exposing your photos is fine. You can under-expose when you want to capture more detail in the highlights and whites than in the shadows. Scenes with lots of contrast where the brightest bits are what’s important often need to be under-exposed. Under-exposing is also useful for capturing the details in the sky during, sunrise, sunset and twilight hours.

Over-exposed

Over-exposure is what happens when more light than necessary hits the camera’s sensor, resulting in a brighter image than what the correct exposure would have created. Photographers often call over-exposed images blown out, or blowing out the highlights. In over-exposed images oftentimes the details in the brightest parts of the image – the highlights and whites – will be lost or blown out, while the details in the shadows and blacks will be preserved.

When to Over-expose

I over-expose my images all of the time. Here are some examples of when you might want to over-expose an image:

  • When details in the highlights and whites don’t matter, but details in the shadows and blacks do.
  • When photographing portraits – especially back lit portraits (or any back-lit subject). You’ll lose the details in the brightest part of the background or sky, but your subject will be exposed for correctly.
  • High-contrast scenes where the details in the shadows are more important than the highlights – I over-expose a lot in my real estate photography to capture exteriors where the house is more important to capture correctly than the sky.

Some Tips for Creating Good Exposures

The final of image of three exposures blended together.

Creating the correct exposure is daunting at first. Here are some tips to help you get there:

Shoot in Aperture or Shutter Priority Modes

I shoot almost exclusively in Aperture Priority Mode. My typical subjects are houses or landscapes so I’m usually shooting on a tripod. I also like to have a wider depth of field for these kinds of subjects. Therefore, it make sense for me to choose my aperture (and ISO) and let the camera do the rest. If you know you need a certain aperture or shutter speed, but it doesn’t matter what the other setting is, shooting in one of the priority modes is a good way to go to make sure you’re getting a good exposure.

Keep Your ISO as Low as Possible

When it comes to exposure, it’s best to let shutter speed and aperture do the heavy lifting. I never leave my ISO setting on Auto and I almost always have it as low as it can be for the scene I’m shooting. The main reason for this is so that digital grain doesn’t get introduced into the image. Another reason is because shutter speed and aperture are the settings that really allow your creativity to shine. If you have the shutter speed and aperture that you want or need for an image and it’s still coming out too dark, then it’s time to bump your ISO up.

Use the Exposure Compensation Button

Most cameras, especially DSLRs and mirrorless cameras have this little button somewhere on the top that lets you compensate your exposure. Just press this little button, spin the dial and you can bump your exposure up or down to get the exposure valuation (EV) you’re looking for, without having to change all of your other settings. Once you’ve adjusted your Exposure Compensation it will adjust the EV for every photo you take until you adjust it again. For instance, if you’re shooting in aperture priority mode and decide that the image is too bright, you can use the exposure compensation button to stop down the exposure valuation. The camera will then adjust your shutter to a faster speed to compensate.

Try Shooting in Brackets

an image of a creek showing three different exposures
The same image correctly exposed on the left, underexposed by 2 stops in the middle, and overexposed by 2 stops on the right. All three exposures were blended together to create one final image.

Brackets are when you shoot the same image at multiple different exposures. Many photographers, especially landscape and architectural photographers will shoot in brackets to ensure they have the correct exposure. Many photographers will also shoot brackets so they can blend them together later in what we call HDR Photography. I primarily shoot brackets for both my landscape, architectural and real estate photography.

Check Your Histagram

A histagram is a little line graph that you can display on your camera’s LCD screen. You’ll also see it in Lightroom when you are editing your photos. Essentially, it’s a graph that plots the brightness of each pixel in your image. The left side of your graph represents the darkest parts of your image, while the right side represents the brightest parts. The Y-axis represents how many pixels are in that particular range. If you’re image is under-exposed the peaks of the graph will be pushed to the left, while if the image is over-exposed the peaks of the graph will be pushed to the right. A properly exposed and balanced image will have most of it’s peaks somewhere in the middle and they won’t be too high.

A histagram is a good way to check your exposure in many photographic situations, however you won’t want to rely on it for every shot. If you’re shooting a scene with lots of highlights and whites the histagram will automatically be pushed to the right side of the graph. The inverse is true for dark scenes.

Exposure Simplified

Creating a good exposure is critical to crafting great photos. However, learning how to do this can be a major challenge. Shutter speed, aperture, and ISO all have a part to play in creating good exposures, as do knowing how to read a scene and expose for it creatively. With a little bit of understanding and a ton of practice, creating good exposures will become second nature in no time. Pretty soon you’ll barely have to think about it.

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Author

Hey there! My name is Leah and I'm a photographer, blogger and wanderer from north Texas. I've been doing photography for nearly a decade now and absolutely love it. My day job is real estate photographer and in my free time you can often find me at a park taking pictures of leaves and flowers. Outside of that my fiance and I love to travel. We spent nine months backpacking through Europe and now spend our free time attempting to plan and going on shorter trips both in the States and abroad.

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