The Evolution Of Cameras: From Concept To Creation

Cameras are incredible tools that allow us to capture and make sense of the world around us. The process of taking a photograph involves capturing light and freezing a moment in time. The basic technology behind this is simple: a still film camera is made of three elements, an optical element (the lens), a chemical element (the film), and a mechanical element (the camera body).

The lens is usually made of glass or plastic and its job is to take the beams of light bouncing off an object and redirect them so they come together to form an image. The film is a light-sensitive material that reacts chemically to light, etching an image on its surface. The camera body is a light-tight box that lets in light at the right moment to capture an image.

The design and manufacture of the lens are critical to the quality of the photos taken. Modern lenses are extremely sophisticated and the ultimate image quality depends on each element in the optical formula being precisely cut, shaped, and polished.

Camera lenses are made by cutting, shaping, and polishing individual glass elements

The design of the lens is crucial to its function. Lenses are optimised to minimise chromatic aberrations, which occur when different waves of light react differently with certain glass shapes. Consumer-grade lenses often feature a spherical design, while professional lenses typically utilise an aspheric shape, resulting in a curved rather than fully rounded lens.

The ability to change focus adds complexity to lens construction. Achieving this function requires multiple pieces of glass that can move back and forth within the lens body. The inclusion of an iris further increases the number of moving parts. Zoom lenses, in particular, tend to have intricate mechanisms with numerous components.

Most lenses are constructed from over 100 individual parts, highlighting the intricate nature of lens manufacturing. While some cheaper lenses are made by injecting molten glass into a die using high pressure, high-precision lenses require the careful grinding and polishing offered by traditional methods.

The camera body is a light-tight box that captures light on film, paper, or a digital sensor

The first cameras used a tiny hole (called a pinhole) in the front of a box to allow in light and to focus the image onto a viewing surface. Today's cameras use glass lenses to focus and capture light much more quickly. When glass elements are used in certain combinations, we can also magnify images.

The camera body is one of the three basic elements of a still film camera, the other two being an optical element (the lens) and a chemical element (the film). The body is the mechanical element that brings together the optical and chemical elements to record a crisp, recognisable image.

The camera body controls the amount of light that reaches a light-sensitive surface inside. The shutter also limits the film's exposure to light by controlling the length of time the film is exposed. Shutter speed can be adjusted in many cameras to suit light conditions and the subject matter.

The diaphragm is an aperture that controls the amount of light entering the camera

The diaphragm is a crucial component of a camera, responsible for controlling the amount of light that enters through the lens. It is a partition in the camera lens with a central hole, known as the aperture, which allows light to pass through. The size of this aperture can be adjusted, determining the amount of light that reaches the film or image sensor.

The diaphragm is composed of a series of overlapping metal plates or blades that can slide across each other, resembling the iris of a human eye. By adjusting the position of these blades, the aperture can be made larger or smaller, thereby controlling the light intensity. This mechanism is known as the iris diaphragm, and it is commonly found in modern DSLR cameras.

The diaphragm can vary in complexity, ranging from a fixed lens with a single aperture size in simple cameras to more advanced cameras with manually or automatically adjustable apertures. The number of blades in the diaphragm can also differ, typically ranging from 2 to 24. The shape of the aperture itself may be circular or polygonal, depending on the number and arrangement of the blades.

The diaphragm works in conjunction with the shutter speed to regulate the exposure of the film or image sensor to light. By controlling the aperture size and the duration of exposure, photographers can manipulate the brightness and darkness of their images. This adjustment is made using the f-stop scale or "F-ratio", which represents the focal length divided by the entrance pupil diameter provided by the diaphragm opening.

In summary, the diaphragm is an essential tool in photography, allowing photographers to control the amount of light entering the camera and ultimately influencing the final image's exposure and lighting.

The shutter controls the length of time the film is exposed to light

The shutter is an essential component of a camera, controlling the duration of light exposure on the film or image sensor. It is a mechanism inside the camera body that functions like a door, opening to let light in and closing to block it. When the shutter button is pressed, the shutter opens, exposing the film or sensor to light, and then promptly closes, ending the exposure. This process is crucial for capturing images with the desired brightness and clarity.

The length of time the shutter stays open, known as the shutter speed, is adjustable and plays a significant role in photography. Shutter speed settings can range from extremely fast speeds, such as 1/8000th of a second, to much slower speeds, like 30 seconds or more with external triggers. The choice of shutter speed depends on factors such as lighting conditions, subject movement, and creative intentions.

Faster shutter speeds are ideal for freezing motion, resulting in sharp images of fast-moving objects. This technique is commonly used in action or sports photography to capture crisp images of birds in flight or racing cars. On the other hand, slower shutter speeds introduce motion blur, creating a sense of movement in the photo. For instance, a long shutter speed can blur the wheels of a speeding car, conveying a sense of speed to the viewer.

Shutter speed also influences the brightness of an image. A longer shutter speed allows more light to reach the film or sensor, resulting in a brighter image. Conversely, a shorter shutter speed reduces the amount of light exposure, leading to a darker photograph. Therefore, adjusting the shutter speed is a critical tool for achieving the desired exposure in various lighting conditions.

In addition to its creative and technical aspects, the shutter's role in limiting light exposure is fundamental to the basic functioning of a camera. By controlling the duration of light exposure, the shutter ensures that the film or sensor captures a clear and well-lit image without being overexposed or underexposed. This balance of light and time is at the heart of photography, allowing photographers to capture and create memorable images.

Film is made of light-sensitive materials that react to light and record an image

Film is a light-sensitive material that reacts to light and records an image. It is the chemical element of a camera, alongside the optical element (the lens) and the mechanical element (the camera body).

Film is made of a chemical emulsion on a plastic substrate that is sensitive to light. When exposed, an analogous image of the scene is created within the chemical layer of the material. The film is coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and resolution of the film.

The emulsion will gradually darken if left exposed to light, but this process is too slow and incomplete to be of any practical use. Instead, a very short exposure to the image formed by a camera lens is used to produce only a very slight chemical change, proportional to the amount of light absorbed by each crystal. This creates an invisible latent image in the emulsion, which can be chemically developed into a visible photograph.

In black-and-white film, there is usually one layer of silver halide crystals. When the exposed silver halide grains are developed, the silver halide crystals are converted to metallic silver, which blocks light and appears as the black part of the film negative. Color film has at least three sensitive layers, incorporating different combinations of sensitizing dyes. Typically, the blue-sensitive layer is on top, followed by a yellow filter layer to stop any remaining blue light from affecting the layers below. Next comes a green-and-blue-sensitive layer, and a red-and-blue-sensitive layer, which record the green and red images respectively. During development, the exposed silver halide crystals are converted to metallic silver, just as with black-and-white film. But in a color film, the by-products of the development reaction simultaneously combine with chemicals known as color couplers to form colored dyes.

In addition to visible light, all films are sensitive to ultraviolet light, X-rays, gamma rays, and high-energy particles.

Frequently asked questions