These three camera and lens parameters interact to determine the amount of light that reaches the light-sensitive surface as well as the sensitivity of that surface. This article explains everything about ISO – when and why you might want to change your ISO settings, and how to do it.
A quick note before we begin: There are no rules about what ISO settings you must use. Every camera manufacturer makes their own recommendations, and some even recommend specific settings based on the type of image being taken. However, there are certain conditions under which each of these functions becomes important. We’re going to cover these in detail later on. For now, let’s focus on understanding exactly how ISO works
Also Read: How to Fix a Blurry DSLR Camera Lens
What is ISO?
ISO stands for International Standards Organization, and it is one of the three main pillars of photography. However, while ISO affects both aperture and shutter speed, it primarily impacts exposure settings.
What Is the Purpose of ISO?
Since shutter speed and aperture, the two traditional exposure controls, don’t provide enough freedom for achieving the ideal exposure in all situations, we revert to ISO. Blur caused by motion is managed by the shutter speed. Sharpness and depth of field are managed by the aperture.
Just having these two limits you to a specific range of shutter speeds and apertures. Very rarely will the image have the proper exposure. ISO was thus designed as a way of controlling exposure values independently of the other two by adjusting the camera’s sensitivity to external light and the level of grain visible in the final image.
Stops of ISO
ISO’s effect on exposure can be quantified in terms of stops. Similar to how doubling the shutter speed doubles the exposure, doubling the ISO doubles the sensitivity of the camera’s sensor. When referring to ISO, a “stop” either doubles or halves the amount of light available.
Exposure will be dark at low ISO settings and bright at high ISO settings. ISO 100 is the most common starting point. In other words, this is the default, or darkest, option, sometimes known as the “base” ISO. ISO 200, the next full stop up, is twice as bright as ISO 100, and ISO 400 is four times as bright as that. To put it another way, there are two stops between ISO 100 and ISO 400, four stops between ISO 100 and ISO 1600, and so on.
This series continues, although it has practical limitations because the threshold changes from camera to camera. In most cases, though, we can get away with an ISO of up to 25600. This translates to an increase of six to eight stops in terms of brightness. As a result, you can achieve proper exposure in conditions that are 64 to 256 times darker than the default setting allows.
Modern digital cameras typically feature even higher settings, but the quality loss makes them essentially useless. Most cameras provide more precision than just full stops when setting the ISO. The standard is to have 1/3 stop adjustments for all exposure settings.
ISO and Noise
To a certain extent, noise grows in tandem with a digital camera’s sensitivity, and subsequent models have a later cutoff for this effect. Noise refers to inconsistencies or oddly lit areas in a picture. This can be mitigated with noise-reduction software, but it will result in a loss of detail.
The ISO setting determines how sensitive the camera sensor is to light, and therefore, how much detail it can capture. A high ISO value allows you to use lower shutter speeds, which lets in more ambient light. But this makes your image grainier because there are more pixels exposed to light.
A low ISO value increases the amount of noise that appears in your photos, making them look softer. And since the number of pixels exposed to light decreases, you don’t get as many megapixels.
In addition, most cameras allow you to adjust ISO sensitivity manually, either via the menu system or by pressing the button directly. You can choose from ISO values ranging from 50 to 6400.
Some cameras feature a menu option called ‘AUTO ISO,’ which allows the camera to automatically adjust the ISO when there is insufficient light to comply with inbuilt rules. It’s a way to improve exposure automatically. While this may seem like a wonderful idea at first, in practice it usually ends up taking away control from the photographer and causing far more issues than it resolves.
If you’re with a photographer and they complain that their camera is acting erratically and ignoring their adjustments, chances are they have Auto ISO engaged. If you reset it, everything will be OK again. Activating this feature on some cameras, such as the vast majority of Nikons, causes the ISO value to be shown in red on the back panel with the image data whenever the ISO value is changed.
How To Adjust ISO Settings?
Most DSLRs have an automatic ISO setting. If your camera doesn’t offer this feature, you can manually set the ISO yourself. Most cameras also let you select from multiple ISO settings. For instance, you might choose ISO 100, 200, 400, 800, or even 1,600. However, there’s no need to go beyond the default setting unless you know exactly what you’re doing.
To change the ISO on your camera:
- Press the Menu button.
- Select Setup/Settings.
- Scroll through the menu until you reach the ISO option.
- Set the desired ISO number.
- Press OK to save the changes.
- Take a test picture with each new setting.
If you’d rather leave the ISO setting up to the camera, here’s how to get started:
- Turn off Auto ISO.
- Choose ISO Sensitivity (Auto).
- Select the lowest ISO setting available.
- Press OK to lock in the setting.
- Test the new setting using the Live View screen.
You may be able to use the Live View screen to help you decide which ISO setting works best for your subject. The Live View screen displays a live preview of whatever scene you’re photographing. It lets you check exposure, focus, white balance, and other settings before taking the actual photograph.
What’s the Difference Between High ISO and Low ISO?
While most photographers agree that increasing the ISO makes images brighter, some people still prefer to shoot at a lower ISO. There are several reasons for this approach. First, shooting at a lower ISO allows you to capture faster action without having to wait for longer exposures. When trying to freeze motion, you’ll often see a difference in quality between shots taken at ISO 1600 and those taken at ISO 3200.
Second, some photographers like to keep noise levels down to preserve detail. Noise is random patterns that appear in pictures that aren’t sharp. Some people believe that increasing the ISO causes noise and reducing the ISO reduces noise. Either way, keeping noise under control requires careful adjustments to the ISO setting.
Lastly, some photographers find that shooting at a low ISO helps them achieve a better depth of field. This means that they can blur out areas of their image that are not important, such as background objects, to create bokeh.
When To Use High ISO
High ISO is one of my favorite features of modern DSLRs. When it works, it makes everything look incredibly sharp. But when should you consider using a high ISO?
15 years ago, raising the ISO above 400 was considered taboo. You could shoot up to 800, but anything above that was considered risky. Today, things are different. A lot has changed since 2007, including the technology inside our cameras.
Today, many DSLRs allow us to raise the ISO far beyond what we used to think possible. In fact, some modern cameras even let us go all the way to 6400. What once seemed like a crazy idea now seems perfectly acceptable.
1. Indoors or at Night
If you take your camera indoors or at night, you’ll often find yourself shooting in low light conditions. And because of this, you won’t be able to capture much detail in your image. This is because the amount of light hitting your sensor isn’t high enough to produce a detailed photo.
In such cases, there are three ways to tackle this issue. You could try to use wider apertures, which would allow more light to hit your sensor. However, while that might make it easier to expose correctly, it can also lead to overexposure.
Another option is to simply turn off autofocus and manually focus your lens. While this might seem like cheating, it actually works quite well.
The last option is to increase ISO sensitivity. By doing so, you’ll be able to collect more light onto your sensor. Unfortunately, increasing ISO sensitivity usually leads to noise issues, especially when working with older lenses.
2. When Using Long Lenses
When you use a long lens, you want to make sure that your exposure settings match your focal length. For example, if you’re taking pictures of wildlife, you might set your ISO at 800, f/2.8, and shoot at 1/500th second. If you’re photographing people in a crowded city street, you might choose a slower shutter speed of 1/30th of a second and increase the ISO to 1600. If you’re shooting sports, you might opt for a faster shutter speed of 1/1000th of a second and lower the ISO even further.
The longer your lens, the harder it is to control how much motion blurs appears in your photo. You need to be aware of camera shake and make adjustments accordingly.
3. When Shooting Fast Paced Objects
If you want to capture action shots without motion blur, you’ll need to increase the shutter speed. But how far do you really need to go beyond what most people are comfortable shooting? Let’s take a look.
The fastest shutter speeds we tend to use are usually around 1/2000s. This is because the human eye cannot detect movement over such short intervals. However, there’s no reason why you couldn’t use even faster shutter speeds to freeze motion. In fact, some photographers shoot down to 1/4000s just to see what happens.
But let’s say you’re trying to photograph something like a running person or a jumping horse. How far can you push things? What about a diver swimming underwater? Can you get away with a slower shutter speed?
The fear of shooting at high ISO is understandable. There are plenty of photographers out there who have shot with ISO levels up to 6400 without incident, and some even go further. If you’re trying to capture a subject that’s moving quickly, don’t be afraid to increase your ISO.
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The best way to determine whether you need to change your ISO setting is to look at the quality of the image you’re capturing. If you notice some graininess or pixelation in your picture, it could mean you need to reduce the ISO setting. On the flip side, if you find yourself struggling to keep your exposure levels consistent across multiple frames, you probably need to raise the ISO.
For example, if you’re photographing a subject against a bright background, you might want to decrease the sensitivity of your camera so the subject stands out more. Or maybe you’re trying to photograph something in dimly lit areas. In these cases, you’ll likely want to increase the sensitivity to let in more light.