The exposure triangle explained in plain language
Aperture, shutter speed and ISO work together to set how bright a photo is. Here is how to balance them and what each one changes creatively.
Every photo is a bucket of light. How full that bucket gets depends on three settings: aperture (how wide the opening in the lens is), shutter speed (how long the sensor is exposed) and ISO (how much the camera amplifies the signal). Change one and you must usually change another to keep the same brightness.
Think in stops
Photographers measure light in stops. One stop doubles or halves the light. Going from f/4 to f/2.8, from 1/250 to 1/125, or from ISO 400 to ISO 800 each adds one stop. Because all three use the same unit, you can trade them: open the aperture one stop and use a shutter speed one stop faster, and the exposure stays the same.
Each setting has a side effect
- Aperture controls depth of field. Wide apertures like f/1.8 blur the background; narrow ones like f/11 keep more in focus.
- Shutter speed controls motion. Fast speeds freeze action; slow speeds blur it.
- ISO controls noise. Higher ISO brightens the image but adds grain, especially in shadows.
A simple way to decide
Start with the setting that matters most for the picture. For a portrait, choose the aperture first. For a moving subject, choose the shutter speed first. Then adjust the other two, keeping ISO as low as the light allows.
Practice exercise
Photograph the same scene three times at the same brightness: once at f/2, once at f/8 and once at f/16, adjusting shutter speed each time. Compare the backgrounds. This single exercise teaches more than any chart.
