Camera ISO Simplified

Camera ISO is probably the easiest to understand compared to shutter speed and depth of field. It's simply, the level of your camera sensor's sensitivity to light - low ISO, means low sensitivity, and high ISO means, high sensitivity. Most modern DSLRs have a base ISO of 100, and it can go up to 4,000,000. To avoid digital noise in images, it's best to use your camera's base ISO most of the time. The only time you should use higher ISOs is when you're shooting in a low light environment.

(Left) Full image @ ISO2000. (right) Image cropped at 100%

What is digital noise? It is the grainy artifact you see in the image caused by increasing the sensitivity of the camera sensor. These grainy artifacts reduce image quality, making it more difficult to optimize through post-production. If you want to avoid grainy images, you will find the camera flash useful to shoot in lower ISOs. On the other hand, modern DSLRs nowadays allow you to shoot in higher ISOs without affecting the overall image quality.

When do you need to change ISO? Well, it depends on the kind of environment you have - this includes the lighting, subjects, and of course, the kind of image you want to capture. Let's say you want to take photos of your kids playing indoors, and you don't want to use flash at the moment. Of course, you make sure to have higher shutter speeds to freeze the moment, and higher F-stop to have everything in-focus. If the image is underexposed, it's best to bump up the ISO until you get the right exposure.

If your camera isn't capable of reducing noise at higher ISOs, you can still get rid of it through third-party applications that you can install in your computer. Adobe Lightroom for example, has a great tool for reducing noise without compromising image quality - just be careful with the settings though. I'll try to make a simple guide about this in the future.