For beginning photographers, one of the hardest parts of learning photography is figuring out all those exposure settings.
You know…aperture, shutter speed, and ISO.
But they don’t have to be these big, scary concepts. Instead, if we break them down, learning how to use them to your advantage is far easier. So, that begs the question: What is ISO in photography?
Well, let’s venture into the world of ISO and learn what it does and how it can impact the look and feel of your images!
Table of Contents
- What is ISO in Photography?
- A Quick Scenario: Brightening Your Images
- A Quick Scenario: Getting a Larger Depth of Field by Using ISO in Photography
- A Quick Scenario: Getting a Faster Shutter Speed
- ISO in Photography: Using ISO When Shooting in Full Auto Mode
- The Artistic Side of ISO: Grain
- How to Decide on an ISO Setting
What is ISO in Photography?
Check out the video above by Apalapse for a detailed introduction to ISO.
Back in the film days, ISO was often referred to as ASA, and it referred to the level of sensitivity of film to light.
The scale on which that sensitivity was measured was 100, 200, 400, and so on, with a lower number indicating a lesser sensitivity to light.
So, if you picked up a roll of ISO 100 film, you understood that it would be most useful for photos taken in bright lighting conditions due to its relative insensitivity to light. You also understood that a roll of ISO 800 film was better suited for lower lighting conditions, like taking photos indoors.
When digital photography came about, the manner in which ISO was measured stayed the same. That means that when you dial in an ISO setting on your camera, 100 is still less sensitive than 200, which is less sensitive than 400, and so on. So, in that regard, ISO in photography remains the same in film and digital applications.
The biggest difference, however, is that where in the film days ISO referred to the physical qualities of the film you used, it now refers to an electronic process inside your camera.
Nevertheless, the concept is still the same – ISO controls the sensitivity of your camera’s sensor to light. It’s just one component of shooting in manual mode with your camera.
A Quick Scenario: Brightening Your Images
Photo by Hryshchyshen Serhii via Shutterstock
Let’s say that you’re indoors taking photos of your kids and that you’re shooting in aperture priority mode (A or Av on your camera’s dial). As the name indicates, aperture priority mode prioritizes the aperture setting in your camera. So, whatever value you dial in, say, f/4, it will remain the same while the camera adjusts the shutter speed accordingly to get a quality exposure.
But let’s say that you find that the images you’re taking are just a little too dark and you want them brightened up.
That’s where ISO in photography comes in.
On many cameras, there’s an ISO button on the top or the back of the camera body that allows you to quickly select a new ISO. So, for example, if your indoor images are too dark when shooting at f/4 and ISO 200, you can switch to ISO 400 to brighten the image.
This works because, with every movement of the ISO value upward, you double the sensitivity of the sensor to light. Of course, the inverse is true as well – with every movement of the ISO value downward, you halve the sensitivity of the sensor to light.
A Quick Scenario: Getting a Larger Depth of Field by Using ISO in Photography
Photo by Mr. Simon Paul via Shutterstock
If you’re in aperture priority mode and you want a larger depth of field (which refers to the area of an image that’s sharply in focus), ISO once again comes in handy.
For example, let’s say you want to create an image like the one above with a large depth of field in which everything from the foreground to the background is in sharp focus.
The problem is that in low lighting conditions, choosing a smaller aperture like f/16 to maximize the depth of field means you restrict the light entering the lens. Doing so in aperture priority mode means that the camera will select a shutter speed to maintain a good exposure.
So, if there’s not a lot of light, that means the camera will select a very slow shutter speed (e.g., two seconds) which could end up being too slow to get a crisp, sharp image if you’re holding the camera in your hand.
Again, ISO can come to the rescue.
If you can’t get the aperture small enough for the desired depth of field without getting a shutter speed that’s too slow, simply increase the ISO. In the scenario above, you might be able to keep the aperture at f/16 by raising the ISO to 1600 (though, these numbers are simply used for illustrative purposes; you’ll need to experiment with the precise settings for the exact shooting situation you’re in).
The increased sensitivity will compensate for the smaller aperture and allow you to shoot with a shutter speed that’s fast enough for you to hold the camera as well. But this is just one example of ISO in photography…
Keep Reading: 5 Unique Exercises to Help Improve Your Photography Skills
A Quick Scenario: Getting a Faster Shutter Speed
Photo by matimix via Shutterstock
Assume that you’re at an indoor event photographing your child playing a sport and that you’re shooting in shutter priority mode. Shutter priority mode allows you to select a shutter speed, and your camera selects an aperture that makes it likely to get a good exposure.
Sports benefit from faster shutter speeds because you can freeze the movement of your subjects, even if they are moving very quickly. So, a shutter speed of 1/1000 seconds might be a good starting point for freezing the movement of your child playing sports.
However, sometimes, the lighting indoors isn’t sufficient for a shutter speed that allows you to freeze movement.
Again, that’s where ISO in photography comes in.
Photo by Zamrznuti tonovi via Shutterstock
Let’s say you try taking a photo like the one above, but the movement of the girl’s arms as she digs the ball is blurry with a shutter speed of 1/500th of a second.
To freeze that movement, you might need to dial in a shutter speed of 1/100th of a second.
The problem is that the change from 1/500th to 1/1000th of a second halves the time the shutter is open. That means you need to compensate for that loss of light somehow.
You can do that by bumping up the ISO – if you’re using ISO 400, changing it to ISO 800 could do the trick. Again, the basic concept of manipulating ISO up or down to help you achieve your goals is what we’re focused on. The precise settings you’ll use will depend on the situation you’re in.
ISO in Photography: Using ISO When Shooting in Full Auto Mode
Photo by hilalabdullah via Shutterstock
When shooting in full auto mode, the camera makes all the decisions regarding exposure settings on your behalf.
That’s nice if you’re just starting out because you don’t have to worry about making constant adjustments to aperture, shutter speed, and ISO.
But, some cameras allow you to override the ISO selected by the camera, giving you greater control over how you use ISO in photography.
This is beneficial for the reasons discussed above – if your images are too dark or your shutter speed is too slow, you can change the ISO.
In the case of shooting in full auto, you simply select the desired ISO to get the desired effect, just as discussed in the scenarios above. If the image is too dark when the camera selects ISO 100, bump it up to ISO 200. If the shutter speed is too slow at ISO 400, bump it up to ISO 800.
Similarly, if you need a smaller aperture to get a larger depth of field, change the ISO value to a larger one.
The Artistic Side of ISO: Grain
Photo by Jorge Elizaquibel via Shutterstock
Back in the film days, the ISO of the film you chose to shoot with had yet another impact on your images. As the ISO value increased, the grainier the resulting images would be. So, if you used ISO 400 film, you’d see more grain in the image than if you used ISO 100 film.
The same concept of ISO in photography applies to today’s digital imaging – the higher the ISO value you select, the grainier the resulting image will be. You can see this in action in the series of images below:
Note the difference in grain from ISO 64, which has no visible grain, to ISO 12,800, which has grain that is plainly evident.
With film photography and digital photography alike, grain can be used as an artistic element. In many cases, the artistic use of grain is used for black and white photography and for images that benefit from adding grittiness, like street photography.
That means that for a traditional portrait or a landscape shot, grain isn’t viewed as positively. That’s because digital grain (usually referred to as noise) lessens the sharpness of the image. In fact, noise can be downright distracting in some photos, as you can see in the series of images above.
Notice how the image on the left is clear, sharp, and crisp, but the image on the right with the highest ISO value has significant noise that detracts from the sharpness of the subject.
Keep Reading: Understanding Aspect Ratio: A Beginner’s Guide
How to Decide on an ISO Setting
Photo by DanJ10 via Shutterstock
ISO in photography comes down to four fundamentals: light, movement, stability, and grain. Here’s a quick refresher:
- In low-light situations, dial in a higher ISO setting.
- To freeze movement, use a higher ISO setting so you can, in turn, use a faster shutter speed.
- If you’re shooting handheld, use a higher ISO setting to help prevent blurry photos, again, because you can use a faster shutter speed.
- If you want a grainy look, use a higher ISO setting.
Conversely, if you have more than enough light – like shooting a portrait outdoors during the day – keep the ISO low so as to minimize digital noise. Likewise, if you’re shooting with a tripod and need to brighten the image, you can use a slower shutter speed to get more light instead of using a higher ISO and dealing with noise.
See ISO in action and learn a little more about how to use ISO in photography in the video above by Photo Genius.
Here’s a final disclaimer: reading up on ISO is just the start! To really grasp how powerful of a tool it can be, you’ll need to get out there and practice manipulating the ISO.
With practice, you’ll develop a better sense of what ISO settings get you what results, and from there you can begin to manipulate ISO with more purpose and confidence.
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Hero photo by Anna Kraynova via Shutterstock
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