Every photograph is the result of light hitting a sensor (or film) for a specific amount of time. Three settings control how much light reaches that sensor: ISO, aperture, and shutter speed. Together they form the exposure triangle — and mastering them is the single biggest leap you can make as a photographer.
Aperture — Control the light and the look
Aperture is the opening inside your lens that lets light through, measured in f-stops (f/1.8, f/4, f/11, etc.). A lower f-number means a wider opening and more light. A wider aperture also produces a shallower depth of field — that blurry background effect called bokeh that looks so good in portraits.
- f/1.4–f/2.8 — Wide open, lots of light, very shallow depth of field
- f/4–f/5.6 — A good all-around range
- f/8–f/16 — Most of the scene in sharp focus, ideal for landscapes
Shutter Speed — Freeze or blur motion
Shutter speed is how long your sensor is exposed to light, measured in seconds or fractions of a second. A fast shutter speed (1/1000s) freezes motion. A slow one (1/30s or slower) can create motion blur — great for silky waterfalls, but bad for sharp handheld shots.
ISO — Sensitivity to light
ISO controls how sensitive your camera's sensor is to light. ISO 100 is the base — clean and detailed. Higher ISO values (800, 3200, 6400) make the sensor more sensitive so you can shoot in darker conditions, but they introduce digital noise (grain) into the image.
Modern cameras handle high ISO much better than older ones, but it's still good practice to keep ISO as low as possible and raise it only when aperture and shutter speed can't give you enough light on their own.
Balancing the three
The art of exposure is in the balance. If you widen your aperture to let in more light, you might need to raise your shutter speed to avoid overexposure. If you increase your shutter speed to freeze motion, you might need to raise your ISO to compensate for the loss of light.
Start by setting the priority that matters most for your shot:
- Shooting portraits? Prioritise aperture (wide, for bokeh).
- Photographing sports? Prioritise shutter speed (fast, to freeze action).
- Landscape at dusk? Use a tripod and keep ISO low.
With practice, adjusting these three settings becomes second nature. The ShutterFox app has scene-specific cheat sheets that tell you exactly where to start for dozens of common situations — so you spend less time guessing and more time shooting.