ISO is how sensitive your camera (specifically the image sensor) is to light.
ISO was originally the term coined to identify the film speed in film cameras based on the ISO system.
The ISO Scale
Most cameras have an ISO scale of 100 – 6400, although different camera brands will occasionally adjust the available scales on certain models.
A typical camera ISO scale would be 100, 200, 400, 800, 1600, 3200, 6400
What does changing the ISO number change in your camera?
Adjusting your ISO setting will change your camera’s sensitivity to light, which will then change you’re the rest of your exposure settings, such as your aperture or shutter speed.
- The higher the ISO number – the more sensitive your camera is to light.
- The lower the ISO number – the less sensitive your camera is to light.
Here is another way to think of how ISO affects your camera: The higher the ISO number, the faster the camera sensor absorbs light.
What does changing the ISO setting change in your image?
Higher ISO settings are great when you need to shoot images in the dark situations, such as churches, wedding receptions or night time images. The trade-off is that the higher your ISO, the more noise your image will have. The more noise your image has, the lower the image quality.
When you increase your ISO setting, your image will get grainer.
- The lower the ISO number – less noise – the finer the image grain.
- The higher the ISO number – more noise – the grainer your image will be.
Here are some comparisons of grain at a few different ISO settings:
200 vs 3200
Here are the images zoomed in. You can see that the reflection of the pear
in the table has significantly more noise at 3200 than 200.
Where do I start with my ISO setting?
Here is a good guideline of where to start your ISO at based on the available light:
|Indoors on a Sunny Day||800|
|Indoors at Night||1600|
|Indoors in Low Light||1600+|
What are some things to consider when selecting your ISO?
Most photographers try to shoot with an ISO that is as low as possible to avoid noise in the photo and to maintain image quality. Here are a few things to consider when selecting your ISO setting:
Are you using a flash?
Using flash will give your image more light during the actual exposure which means you may be able to decrease your ISO setting.
Are you using a tripod?
Tripods help stabilize your camera so you can take a longer exposure without blur, which means you can go with a lower ISO resulting in a less grainer image.
What are my other camera settings?
If one of your other camera settings is the most important setting for the image that you are taking, for example you want a fast shutter speed to capture movement, than adjust your ISO setting to help set the optimal balance for the most important part of the exposure.
Written by Guest Contributor: Nikole Bordato