Exposure Triangle Trainer
Pick the light you are shooting in, then balance aperture, shutter speed and ISO until the picture is correctly exposed. Notice what each choice does to depth, motion and noise.
Too bright: 1.0 stop over
What each setting is doing to the picture
The light, and your settings
Aim for “Correct exposure”. Every step on these sliders is one stop: a stop up lets in twice the light (a bigger opening, a slower shutter, or a higher ISO), a stop down half. You can reach the same exposure many ways; each way changes depth, motion or noise differently.
Challenge
- Bright sun: get the correct exposure at f/16 (the “sunny 16” rule says 1/ISO seconds).
- Concert stage: freeze movement (1/250 or faster) without going over ISO 6400.
- City at night, handheld: keep the shutter at 1/60 or faster. What do you give up?
The three settings
- Aperture is the size of the lens opening, written as an f-number. A smaller number is a bigger opening: more light and a thinner zone of sharpness.
- Shutter speed is how long the sensor collects light. A fast shutter (1/1000 s) freezes movement; a slow one (1/15 s) lets it blur and lets in more light.
- ISO is how strongly the sensor signal is amplified. A higher ISO makes the picture brighter in dim light but adds noise.
Stops
Photographers measure light in stops. One stop up doubles the light and one stop down halves it. Each full step on the aperture, shutter and ISO scales is one stop, which is why you can trade them: open the aperture by one stop and speed the shutter up by one stop, and the exposure stays the same while the look changes.
A starting point: sunny 16
On a bright, sunny day, f/16 with a shutter speed of one over your ISO (1/100 s at ISO 100) gives a good exposure. Open the aperture by a stop and speed up the shutter by a stop as the light gets weaker or the subject moves faster, and raise ISO only when you have to.
Exposure questions
What is a stop of light?
A doubling or halving of the amount of light. Going from f/4 to f/2.8, from 1/250 s to 1/125 s, or from ISO 400 to ISO 800 each lets in twice as much light.
What shutter speed should I use?
It depends on the movement. For a handheld camera, a shutter speed of about one over the focal length (1/50 s for a 50 mm lens) or faster avoids blur from shake. Walking people need about 1/250 s, running or sport 1/1000 s or more, and birds in flight 1/2000 s or more.
What ISO should I use?
The lowest ISO that still lets you use the aperture and shutter speed you need. Modern cameras handle ISO 1600 or even 6400 well, and a sharp, slightly noisy picture is better than a clean, blurred one.
Why is my picture noisy in the dark?
Less light means a weaker signal, and raising the ISO amplifies the noise along with it. A wider aperture or a slower shutter speed gives the sensor more light so you can keep the ISO lower.
Should I shoot in manual mode?
Manual mode gives you full control and is the best way to learn how the three settings work together. Many photographers then move to aperture priority or shutter priority with exposure compensation for everyday shooting.