Beginner's Guide
The Exposure Triangle Explained
Three settings control the light in every photograph: shutter speed, aperture, and ISO. The exposure triangle is how they work together.
What Is the Exposure Triangle
The exposure triangle is the relationship between shutter speed, aperture, and ISO. These are the only three settings that control how much light reaches your camera's sensor. Change one, and you need to compensate with the others to keep the same brightness.
Each setting also has a creative side effect. Shutter speed controls motion blur. Aperture controls depth of field. ISO controls image noise. The exposure triangle is about balancing all three to get the light and the look you want.
Shutter Speed
Shutter speed is how long the sensor is exposed to light. Measured in fractions of a second.
- ■1/1000s - freezes fast action. A bird mid-flight, water droplets suspended in air. Very little light gets in.
- ■1/250s - general handheld shooting. Enough to keep things sharp without a tripod.
- ■1/30s - motion blur appears. Moving subjects streak across the frame. Lots of light gets in.
- ■2s+ - long exposure territory. Light trails from cars, silky water, star trails. Needs a tripod. See our night photography settings guide for more on this.
Faster shutter = less light, frozen motion. Slower shutter = more light, motion blur. That's the trade-off on this side of the triangle.
Aperture
Aperture is the size of the opening in your lens. Measured in f-stops. The numbering is backwards from what you'd expect.
- ■f/1.8 - f/2.8 - wide open. Lots of light, very shallow depth of field. The subject is sharp, the background melts into a soft blur. This is the classic portrait look.
- ■f/5.6 - f/8 - middle ground. Good sharpness across more of the frame. Works for group shots and general photography.
- ■f/11 - f/16 - small opening, less light. Everything from foreground to background is sharp. Landscape photographers live here.
Lower f-number = bigger hole, more light, blurrier background. Higher f-number = smaller hole, less light, more of the scene in focus. For more on using aperture in portraits, see the portrait photography tips guide.
ISO
ISO controls how sensitive the sensor is to light. It's the setting you adjust when shutter speed and aperture alone can't get enough light.
- ■ISO 100-400 - clean, noise-free images. Use this in daylight or bright conditions.
- ■ISO 800-1600 - light grain starting to appear. Indoor shooting, overcast days, shade.
- ■ISO 3200+ - visible grain. Low light, concerts, night shooting. Modern cameras handle this better than older ones.
Keep ISO as low as your scene allows. Raise it when you need to. A slightly grainy photo is always better than a blurry one from a shutter speed that was too slow. If you're choosing a camera and noise performance matters, our best camera for beginners guide covers sensor sizes and low-light capability.
How the Three Settings Work Together
Every photo is a light problem. The exposure triangle is how you solve it. The three settings are connected: change one, and the exposure shifts. You compensate with the others.
Example: Bright day at the park. ISO 100 (plenty of light, keep it clean), f/5.6 (moderate depth of field), 1/500s (freezes motion). Light is abundant, so everything stays fast and low.
Example: Dim restaurant.ISO 3200 (sensor needs the sensitivity), f/2.8 (wide open for maximum light), 1/60s (slow enough for light, fast enough to avoid shake). You're trading image cleanliness for a usable photo in low light.
Example: Portrait at golden hour. ISO 200 (golden hour has great light), f/2.8 (wide open for background blur), 1/250s (sharp subject). Aperture is doing the creative work here, shutter speed and ISO just follow along. More on golden hour light in the golden hour photography guide.
The pattern is always the same: decide what matters most for the shot (freezing motion? background blur? low noise?), set that first, then balance the other two.
Learning the Triangle: One Setting at a Time
Trying to learn all three settings at once is the slow way. The faster approach: lock two, learn one.
Set aperture to f/4 and ISO to 800. Don't touch them. Spend an hour changing only shutter speed and watching how it affects brightness and motion. Once shutter speed feels natural, unlock aperture as a second variable. Then add ISO last.
By the time you're using all three, each one already makes sense on its own. No overwhelm.
This is the one-setting-at-a-time method used in the DJB Photography School course. The full breakdown is in the learn manual photography guide, with step-by-step exercises for each setting.
Quick Answers
What is the exposure triangle in photography?
The exposure triangle is the relationship between shutter speed, aperture, and ISO. These three settings control how much light reaches the camera sensor. Adjusting one affects the others. Balancing all three gives you correct exposure and creative control over motion, depth of field, and image noise.
Which exposure triangle setting should I learn first?
Shutter speed. It has the most visible effect on your photos (motion blur vs frozen action) and it's the easiest to understand. Lock aperture at f/4 and ISO at 800, then practice with shutter speed only.
Does the exposure triangle apply to phone cameras?
Yes. Phone cameras use the same three settings internally. Most phone camera apps handle them automatically, but pro/manual modes on phones give you direct control over shutter speed, ISO, and sometimes aperture simulation.
What happens if one setting is wrong?
The photo will be too bright (overexposed) or too dark (underexposed). Too much light from any combination of the three settings blows out highlights. Too little light makes the image muddy and dark. The exposure meter in your viewfinder shows you when the balance is right.
Practice with a Camera in Hand
Reading about the exposure triangle is a start. The next step is using it. The DSLR & Mirrorless Express Photography Course in Melbourne covers the exposure triangle in a 3-hour hands-on session, capped at two students. You'll adjust shutter speed, aperture, and ISO on your own camera while shooting in Melbourne CBD.
Got questions about the course? Check our frequently asked questions. Once you're confident with manual mode, the next step is learning to edit. Our Lightroom course for beginners covers everything from importing to RAW development.