Capturing light
A camera captures images by letting light in through a small opening and recording it on film or an electronic sensor. Photography lets us save memories, report news, study science and create art. Today, billions of people carry cameras in their phones.
The camera obscura
Long before photographs, people knew about the camera obscura (Latin for "dark room"). Light passing through a tiny hole into a dark room projects an upside-down image of the outside scene on the opposite wall.
| Time | Development |
|---|---|
| About 400 BCE | Chinese philosopher Mozi describes the pinhole effect |
| About 1000 CE | Arab scientist Ibn al-Haytham explains how it works |
| 1500s–1600s | Artists use camera obscura boxes with lenses to trace scenes |
The problem: there was no way to keep the image.
The first photographs
| Year | Inventor | Development |
|---|---|---|
| 1826–1827 | Joseph Nicéphore Niépce (France) | Oldest surviving photograph, View from the Window at Le Gras; the exposure took hours or even days |
| 1839 | Louis Daguerre (France) | Daguerreotype: sharp images on silver-coated copper plates; exposures of a few minutes |
| 1841 | William Henry Fox Talbot (England) | Calotype: paper negatives that could make many copies |
| 1851 | Frederick Scott Archer | Wet collodion glass plates; faster and sharper |
| 1888 | George Eastman (USA) | Kodak box camera with roll film: "You press the button, we do the rest" |
| 1900 | Kodak Brownie | Cost $1; made photography affordable for families |
| 1935 | Kodachrome | Popular colour film |
| 1948 | Polaroid | Instant photos developed in minutes |
| 1975 | Steven Sasson (Kodak) | First digital camera; 0.01 megapixels, took 23 seconds to record one image |
| 2000s | Camera phones | Cameras become part of everyday phones |
Early portraits required people to sit perfectly still for minutes, which is one reason people rarely smiled in old photos.
How a camera works
| Part | Job | Like your eye |
|---|---|---|
| Lens | Focuses light into a sharp image | Lens and cornea |
| Aperture | Opening that controls how much light enters | Pupil |
| Shutter | Opens for a set time to let light in | Eyelid |
| Film or image sensor | Records the image | Retina |
| Viewfinder or screen | Lets you frame the picture |
The lens forms an upside-down image, just like your eye does.
Exposure
Three settings control how bright a photo is:
| Setting | Effect |
|---|---|
| Aperture size | Bigger opening = more light and a blurrier background |
| Shutter speed | Slower = more light, but moving objects blur; faster freezes motion |
| ISO (sensitivity) | Higher = brighter in low light, but more grainy |
Photographers balance these three to get the photo they want.
Film vs. digital
| Film | Digital |
|---|---|
| Light-sensitive chemicals change when exposed | An image sensor converts light into electrical signals |
| Must be developed with chemicals | Images are ready instantly |
| Limited shots per roll | Thousands of photos on a memory card |
| Images made of pixels |
Digital sensors
A digital sensor has millions of tiny light-sensitive spots. Each records brightness. Filters in a pattern of red, green and blue let the camera work out colours. A megapixel is one million pixels. Phone cameras today often have 12 to over 100 megapixels.
Canadian scientist Willard Boyle, born in Amherst, Nova Scotia, co-invented the CCD (charge-coupled device) image sensor in 1969 with George Smith. They shared the 2009 Nobel Prize in Physics. CCDs made digital cameras, the Hubble Space Telescope’s images and many medical scanners possible.
Uses of cameras
| Area | Use |
|---|---|
| Journalism | Documenting events and history |
| Science | Telescopes, microscopes, wildlife trail cameras |
| Medicine | Endoscopes, dental and eye imaging |
| Security | Surveillance cameras |
| Space | Satellites photographing Earth; rovers on Mars |
| Art and memories | Portraits, landscapes, family photos |
Photography and responsibility
Cameras raise questions about privacy and honesty. Always ask before photographing people, and be aware that digital photos can be edited or faked.
Common mistakes
- Thinking photography was invented in one step. It developed over centuries.
- Thinking more megapixels always means better photos. Lens quality, sensor size and lighting matter too.
Try it yourself
- Make a pinhole camera from a shoebox or a tube with foil and tracing paper. Point it at a bright window. Is the image upside down?
- Take the same photo with your phone in bright light and dim light. Compare the quality.
- Find the oldest photograph in your family. How was it made?
Quick recap
- The camera obscura projected images centuries before photography.
- Niépce made the first surviving photo in the 1820s; Daguerre and Talbot followed.
- Eastman’s Kodak made photography popular.
- Cameras use a lens, aperture, shutter and film or sensor.
- Canadian Willard Boyle co-invented the CCD sensor behind digital imaging.