What is ISO in Photography?
ISO controls your camera sensor’s sensitivity to light. A lower ISO (like 100) means less sensitivity, resulting in cleaner images, while a higher ISO (like 3200 or above) boosts sensitivity but introduces grain, also known as digital noise. It’s one of the three exposure settings — along with shutter speed and aperture — that determines how bright or dark your photo turns out. The goal? Use the lowest ISO possible for the cleanest image, unless the light says otherwise.
Why ISO Matters More Than You Think
ISO isn’t just a number — it’s a decision. A low ISO keeps your images crisp and smooth, ideal for bright conditions. But in low light, raising your ISO can mean the difference between a shot and a missed moment. Modern cameras handle high ISO better than ever, but every increase still adds some grain. It’s all about finding the balance between brightness and clarity.
When to Adjust ISO (and When Not To)
Use low ISO (100–200) for daylight, well-lit scenes, or when using a tripod. Bump it up (800–3200+) for low light, indoor shoots, or fast-moving subjects when you need a quicker shutter speed. Just be mindful: the higher you go, the more noise you’ll get. If you're shooting in RAW, you’ll have a bit more flexibility to clean it up later — but don’t rely on that as a crutch.
ISO and the Exposure Triangle
ISO is one leg of the exposure triangle — the other two being shutter speed and aperture. Raise ISO to compensate for low light when you can’t slow your shutter or open your aperture further. Lower ISO when light is abundant, or when you want maximum image quality. Mastering ISO means knowing when to use it and when to let your other settings do the work.