The very first cameras were called the camera obscure, which is now known as a pinhole camera. These cameras relied on very basic principles; light would pass through an extremely narrow hole to project their image on the surface inside.
In much the same way that you can hear a person outside your room, light from outside can be diffracted inside a room. The only difference is that the entrance must be quite small for light as compared to sound.
The equation that describe single slit diffraction is
(d)sinθ= λ
where d is the distance that the light diffracts in between, lambda is the wavelength of light and theta is the angle between the normal and the bent wave.
In 1888, George Eastman invented film, and the disposable camera. This was following an era where people used glass daguerreotypes, and burned image into film using a special chemical process.
Film photography used a process where the chemicals on the plastic strips reacted with light to form an image. The more light, the more the chemicals will react and the brighter the image will appear. Film was used until the late 90s, when digital cameras started to take over. However, digital cameras had been around since 1975 when an engineer from Kodak invented them.