What is ISO in Photography - Guide for Beginners
In this guide, we will introduce ISO for beginners and explain how to use it effectively.
What is ISO?
In very basic terms, ISO is simply a camera setting that will brighten or darken a photo. As you increase your ISO number, your photos will grow progressively brighter. For that reason, ISO can help you capture images in darker environments, or be more flexible about your aperture and shutter speed settings.
However, raising your ISO has consequences. A photo taken at too high of an ISO will show a lot of grain, also known as noise, and might not be usable. So, brightening a photo via ISO is can be a trade-off. You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead (for example, if using a longer shutter speed would cause your subject to be blurry).
Common ISO Values
Most cameras use a standard scale, doubling each step:
100, 200, 400, 800, 1600, 3200, 6400…
Low vs High ISO Noise Visibility
A image at ISO 3200 has much more noise than the one at ISO 200. This is why you should avoid high ISOs whenever possible, unless conditions require you to use them.
How to Change ISO
Changing ISO varies from camera to camera. Here are some common ways to change ISO:
- To start, enter a mode that lets you select the ISO yourself. Get out of Auto mode, and go to Manual, Shutter Priority, Aperture Priority, or Program (we tend to prefer Aperture Priority or Manual).
- For entry-level DSLRs and mirrorless cameras, you probably need to open a menu (possibly the “quick menu”) and find the section for ISO. Select the value you want, or set it to Auto.
- For higher-end cameras, there may be a dedicated “ISO” button on the camera. Press it while spinning one of the wheels to change your ISO setting. If you don’t see a button labeled “ISO”, it is still possible that your camera will let you program one to perform this task.
- Other cameras may have a dedicated wheel that already has various ISO settings marked. This makes things even easier.
Check your camera manual if you still aren’t sure. However, it is worth being very familiar with how to change your ISO setting quickly, since it’s something you will likely be adjusting quite often, especially if you shoot in low light conditions without a tripod or flash.
When to Use Low ISO
You should always try to stick to the lowest ISO of your camera, which is typically ISO 100 or 200, whenever you can. If there is plenty of light, you are free to use a low ISO and minimize the appearance of noise as much as possible.
Even in dim or dark environments, you still might be able to use a low ISO. For example, if you have your camera mounted on a tripod or sitting completely still on a table. In that case, you can safely use a low ISO and brighten your photo via a long shutter speed instead, since you won’t introduce camera shake. However, keep in mind that if your camera does use a long shutter speed, anything that is moving will look like a ghost or have motion blur.
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Quick ISO Reference
ISO 100–200
Best for bright daylight or studio lighting. Produces the cleanest, sharpest images with almost no noise.ISO 400–800
Good for indoors with decent lighting, cloudy days, or golden hour. Slight noise may appear, but image quality is still very high.ISO 1600–3200
Useful for low-light situations such as concerts, indoor sports, or nighttime photography without a tripod. Noise becomes noticeable, but the photo is still usable.ISO 6400 and above
For very dark environments where you must capture the shot (e.g., astrophotography, dim indoor events). Expect significant noise, but it’s often better than missing the photo entirely.
When to Use High ISO
Even though it is ideal to use low ISOs, there will be plenty of times when a high ISO is necessary in order to take a good photo in the first place. The simple reason is that you are often fighting against motion blur, and you will need to pick between a sharp photo at a high ISO, or a blurry photo at a low ISO. I would prefer a sharper photo. High ISO is common when taking pictures of birds or some sports. If you have a modern camera made in the last 4 years and it’s a higher-end then it can actually probably handle higher ISO then you think. Go try it out on non-moving items then on moving things.
On most cameras, there is a setting for Auto ISO, which works great in low-light environments. The beauty of this setting is that you input the maximum ISO you are willing to use, so that the camera does not cross that limit. Personally, if I want to limit the amount of noise in a photo, I will set my maximum ISO to something like ISO 1600, or 3200. The downside is that the camera will start using progressively longer shutter speeds if it reaches these ISO limits, which leads to more motion blur.
Some photographers think that the best way to capture high-quality images is to use lowest ISO 100% of the time. Don’t try to force ISO 100 in a dark environment, or your photos will come out way too dark and lose details.
FAQ
Is ISO “Sensor Sensitivity”?
This is the most common myth related to ISO. It is something you will see all over the web (and in print). However, although it may help you to think of ISO as “acting like” camera sensor sensitivity, that’s not what it actually does. Instead, digital sensors only have a single sensitivity, regardless of your ISO. It is more accurate to say that ISO is like a mapping to tell your camera how bright the output photo should be, given a particular input exposure.
Is Raising ISO Just Like Brightening Your Photo on a Computer?
This is an insightful point, but it’s based on a common misconception. Brightening a photo on your computer can resemble increasing your ISO, as it enhances brightness and makes noise more apparent. However, raising your ISO in-camera typically yields better image quality than significantly brightening an ISO 100 photo in post-processing software like Lightroom. It’s preferable to use ISO 800 when needed instead of over-brightening an ISO 100 image.
What is the Best ISO Setting for Low-Light?
In low-light conditions, your shutter speed often slows down, which can cause camera shake or motion blur. To mitigate this, consider raising your ISO setting to a higher value, like ISO 1600. Depending on your aperture and lighting, you may need to increase the ISO further. This also good reason to also shoot in RAW.
— Spencer Cox1