Understanding ISO in Photography – A Beginner's Guide to Better Exposure

nikkikearns
May 8
2 min read

If you're starting out in photography or looking to improve your manual shooting skills, understanding ISO is essential. ISO is one of the three key pillars of the exposure triangle (along with shutter speed and aperture), and knowing how to use ISO settings effectively can make a big difference in your image quality.

Let’s break ISO down in simple, beginner-friendly terms so you can feel confident using it in your photography.

What Is ISO in Photography?

ISO controls your camera sensor’s sensitivity to light. Lower ISO values like 100 or 200 are best used in bright conditions, such as shooting outdoors in daylight. Higher ISO values like 1600 or more are useful in darker settings where more light sensitivity is needed.

Think of ISO like turning up the volume on a quiet sound. The quieter the environment (low light), the more you need to amplify it (increase ISO) to "hear" the details.

How to Use ISO Settings

Here’s a quick guide to help you know when to adjust ISO:

☀️ Bright light (sunny days): ISO 100–200
☁️ Cloudy or indoor light: ISO 400–800
🌙 Low-light or night scenes: ISO 1600+

As your ISO goes up, your camera becomes more light-sensitive, which lets you use faster shutter speeds or smaller apertures in low-light situations.

Does ISO Create Noise in Photos?

A common misconception is that ISO causes noise. The truth is, ISO doesn’t create noise—it just reveals it. The real source of noise comes from your exposure conditions, such as low light or long shutter speeds.

When you increase ISO, you're brightening the image signal, and with it, any imperfections (noise) that were already there. So yes, higher ISO can mean more visible grain, but it’s not the villain—it’s just doing its job.