Every camera operates on the basic principle that light passes through a lens onto a light-sensitive surface. The shutter controls the exposure time, while the sensor or film records the image. The camera obscura is the original form of the camera. Digital cameras use a sensor and memory card, while analog cameras use film.
Category: Photography Basics > 2. Camera Technology & Construction Article ID: 2.1 Created: May 2026
Key Points in Brief
- Every camera—analog or digital—works on the same basic principle: light passes through a lens onto a light-sensitive surface
- The lens focuses the light, the shutter controls how long it falls, and the sensor or film records the image
- The camera obscura (pinhole camera) is the original form of this principle—it has existed since ancient times
Explanation
The Basic Structure of Every Camera
Whether it’s a smartphone, compact camera, or DSLR, all cameras share the same basic components:
| Component | Function |
|---|---|
| Lens | Focuses the light and creates a sharp image of the subject |
| Shutter | Opens for a defined period, allowing light onto the sensor/film |
| Sensor (digital) / Film (analog) | Registers the light and stores the image |
| Viewfinder / Monitor | Shows the photographer the framing before and after the shot |
| Shutter Release | Triggers the shot and opens the shutter |
Step by Step: How a Photo is Created
- The photographer points the camera at the subject and selects the framing via the viewfinder or monitor
- They press the shutter release
- The shutter opens for a brief moment (the exposure time)
- Light passes through the lens and is focused on the sensor or film—the image is formed
- The shutter closes again
- The image is stored—immediately on the memory card for digital cameras, or as a chemical change on the film for analog cameras
The Lens: the “Eye” of the Camera
The lens consists of multiple lenses that together act like a convex lens. The light is focused in such a way that a sharp, reduced image of the subject is formed on the sensor—in technical terms, this image is initially upside down, which the camera automatically corrects internally.
Depending on the design and focal length of the lens, the size of the captured area and the spatial effect of the image vary. More on this in the article about focal length (→ 2.6).
The Pinhole Camera: the Original Principle
The simplest form of a camera is the camera obscura (Latin for “dark chamber”)—a light-tight box with a tiny hole on one side. Light passes through the hole and creates an upside-down image of the subject on the opposite inner wall.
This principle has been known since antiquity (Aristotle already described it) and is the direct predecessor of every modern camera. When the hole is replaced by a lens, a sharper and brighter image is produced—this marks the step to the actual photographic camera.
Digital Camera vs. Analog Camera: What’s Different
In analog cameras, the inserted film simultaneously captures and stores the image. In digital cameras, these functions are separated: an electronic image sensor captures the image, and a memory card stores it as a file. Digital cameras additionally have a monitor for instant image review and ports for transferring photos.
Practical Tip
The basic principle of the camera can be easily experienced yourself: take a dark box, poke a tiny hole in one side with a needle, and look inside from the opposite side in a dark room. The image of the subject in front of the hole appears—upside down—on the back wall. Welcome to the world of the camera obscura.