Mastering the 3 Keys of Photography: ISO, Aperture & Shutter Speed (And How They Work Together)
When I first picked up a camera, I didn’t know the difference between ISO and espresso. All I knew was that some photos looked how I imagined, and others... not so much. I thought it was about getting lucky with lighting or just copying someone else's settings. But the truth is, understanding the three core settings—ISO, aperture, and shutter speed—changes everything.
This blog is your crash course in what I like to call the three keys to photography. These settings are the foundation of almost every photo you take. And once you really get how they work—and how they dance together—you stop guessing and start creating.
The Exposure Triangle: The Foundation
These three settings form what photographers call the exposure triangle. Think of it like this:
ISO = Sensitivity
Aperture = How much light gets in
Shutter Speed = How long the light hits the sensor
Adjust one, and it affects the others. Your job? Find the perfect balance between all three, depending on what kind of shot you're going for.
1. ISO – Light Sensitivity
ISO tells your camera how sensitive it should be to light.
Low ISO (like 100 or 200) = Less sensitive to light → cleaner, sharper image
High ISO (like 1600 or 3200) = More sensitive to light → brighter image but more noise (that grainy look)
Use low ISO when:
You're shooting outside in bright light
You want the cleanest possible image
Use high ISO when:
It’s dark
You’re indoors or shooting at night
You need to brighten the shot but can’t adjust shutter or aperture any further
Pro tip: Don’t be afraid to raise your ISO if you need to. A noisy shot is better than a blurry one. Especially when it’s a once-in-a-lifetime moment.
2. Aperture – The Eye of Your Camera
Aperture is the opening inside your lens that lets in light. It’s measured in f-stops (f/1.8, f/4, f/11, etc.), which can be a bit weird at first because smaller numbers mean bigger openings.
Wide aperture (like f/1.8) = More light + shallow depth of field → blurred background, great for portraits
Narrow aperture (like f/11 or f/16) = Less light + deeper focus → everything in frame is sharp, great for landscapes
This is where your creative style starts to come in. Want that dreamy background blur (also called bokeh)? Go wide. Want everything from foreground to mountains in focus? Stop it down.
Remember: Every time you adjust the aperture, you’re also changing how much light hits the sensor, so you may need to balance it out with ISO or shutter speed.
3. Shutter Speed – Time & Motion
Shutter speed controls how long your camera’s shutter stays open.
Fast shutter speed (1/1000s) = Freezes motion → great for sports, wildlife, action
Slow shutter speed (1/10s or slower) = Captures motion → great for waterfalls, light trails, low light
But here’s the trade-off: slower shutter speeds let in more light but also increase the risk of blur. If your hand shakes, or your subject moves, the shot could end up soft.
Handheld tip: Try to keep your shutter speed at least as fast as the focal length of your lens. So if you’re shooting at 50mm, keep it at 1/50s or faster.
How They All Work Together
This is the fun (and slightly brain-melting) part: these three settings constantly affect each other.
Let’s say you're shooting a portrait in soft natural light. You want a blurry background, so you choose f/2.0. That lets in a lot of light, so to balance it:
Drop your ISO to 100 or 200 to avoid overexposure
Use a fast shutter speed to freeze motion and avoid blur
But now imagine it’s getting darker. You need more light. You could:
Open your aperture more (if possible)
Slow your shutter (but watch for blur)
Raise your ISO (but watch for noise)
Every change is a trade-off. The goal is to choose which setting matters most for the look you want—and then adjust the others to get the exposure right.
Bonus: Composition & Depth of Field
Let’s say you’ve nailed exposure. That’s the technical side. But to make your photos interesting—not just technically correct—you need to think about composition and depth of field.
Composition Tips:
Rule of thirds: Place your subject off-center for a more dynamic image
Leading lines: Use roads, fences, or shadows to draw the eye
Framing: Shoot through objects to frame your subject
Fill the frame: Get close and focus on details
Negative space: Give your subject room to breathe
Depth of Field (DOF)
DOF is how much of your image is in focus from front to back. It’s mostly controlled by aperture, but also by distance to your subject and focal length.
Shallow DOF (blurry background) = Wide aperture + close to subject + long lens
Deep DOF (everything sharp) = Narrow aperture + farther from subject + wide lens
You don’t always need to blur the background to make a good photo. Sometimes having everything sharp tells a more complete story—like in street or landscape photography.
Final Thoughts: Keep It Simple at First
Here’s the thing: photography can feel overwhelming when you’re juggling three settings every time you press the shutter. But if you start with one at a time—say, always using aperture priority and letting the camera choose shutter—you can build confidence fast.
And eventually, you won’t even think about it. You’ll feel what settings are right. That’s when you go from snapping pics to actually creating images with intent.
Your Next Step: Try This Out
Go outside, pick one subject, and take 10 photos while only adjusting one setting at a time. See how it changes the final result.
