Updated: Oct 9, 2022
Camera ISO is a critical setting, but it is NOT part of exposure
By using a high ISO setting here, I was able to select a fast shutter speed and freeze the birds in flight.
ISO is one of the three pillars of photography (the other two being shutter speed and aperture), and it has a major effect on your images. How does camera ISO affect your images? In this article, we will introduce ISO for beginners and explain how to use it effectively for the best possible results.
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 always 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).
Note how much brighter the image gets when ISO is increased from 100 to 1600
What is the Meaning of ISO?
The acronym ISO stands for “International Organization for Standardization”. However, camera ISO does not directly refer to the organization that creates various technology and product standards. Ever since two film standards called ASA and DIN were combined into ISO standards in 1974 (later revised for both film and digital photography), they were referred to as one word “ISO” from that point on. Although ISO initially defined only film sensitivity, it was later adopted by digital camera manufacturers with the purpose of maintaining similar brightness levels as film.
Common ISO Values
Every camera has a different range of ISO values (sometimes called ISO speeds) that you can use. A common set is as follows:
ISO 100 (low ISO)
ISO 6400 (high ISO)
Quite simply, when you double your ISO speed, you are doubling the brightness of the photo. So, a photo at ISO 400 will be twice brighter than ISO 200, which will be twice brighter than ISO 100.
What is Base ISO?
The lowest native ISO on your camera is your “base ISO”. This is a very important setting, because it gives you the potential to produce the highest image quality, minimizing the visibility of noise as much as possible. Some older DSLRs and a number of modern cameras, such as the Fuji X-T2 have a base ISO of 200, whereas most modern digital cameras have a base ISO of 100. Optimally, you should always try to stick to the base ISO to get the highest image quality. However, it is not always possible to do so, especially when working in low-light conditions.
Side note: Some cameras have extended “HI” and “LO” values for ISO that might stretch beyond their native range. However, these are completely simulated and lower your image quality. We recommend avoiding them.
Low vs High ISO Noise Visibility
To give an example of two photos taken at different ISO values, take a look at the comparison below. Pay attention to the level of noise (graininess and blotchy colors) in the images: