How does a camera work?
Welcome! I am so excited to help you explore the mechanics of photography. To make sure we tailor our time to exactly what you need, what sparked your interest in cameras, and what are you hoping to understand most?
I'm curious about the physics of how light becomes a picture.
Let's start our journey into the physics of photography right at the beginning. It is actually much simpler than you might think: every camera, from a giant 19th-century wooden box to the tiny lens on your smartphone, is fundamentally just a light-proof box with a small hole in it.
Your path
Core Camera Components
Digital vs. Analog Capture
The Physics of the Light-Proof Box
To understand how this setup creates an image, we first have to look at how light behaves in the wild. Light travels in straight lines. When sunlight or lamplight hits an object—like a red apple—the light bounces off it in every direction.
If you place a piece of paper next to that apple, the paper does not show an image of the apple. Instead, it just looks white. This is because light rays reflecting from the top, middle, and bottom of the apple are all hitting every single spot on the paper at the same time. The rays overlap and scramble together, creating a wash of white light rather than a coherent picture.
To fix this, we need to sort those light rays out. This is where our light-proof box, historically known as a , comes in.
By putting a tiny pinhole in one side of a dark box, we block almost all the scrambled light rays. Only a highly select few can pass through. A ray reflecting off the very top of our apple can only travel in a straight line through the hole, landing near the bottom of the opposite wall. Meanwhile, a ray reflecting off the bottom of the apple passes through the hole and lands near the top of the wall. Because the light rays cannot overlap anymore, they paint a perfect, upside-down image of the apple on the back wall of the box!
An upright red arrow on the left projects an inverted, faded red arrow onto the inner right wall of a dark box via straight light rays intersecting at a central pinhole.
That beautiful, inverted projection is the starting point of every photo. But as you might imagine, a tiny pinhole lets in very little light, which makes the image incredibly dim.
Our next challenge is finding a way to make this image bright and sharp.