Basic Photography/The camera
- 1 Origins of the camera
- 2 Cameras
- 3 Lenses
- 4 Notes
Origins of the camera
Someone's god allegedly said...
"Let there be light!" Most philosophies, religious or otherwise, presuppose some sort of creation myth. For scientists it's a big bang, for monotheists the big guy upstairs, and for other traditions it can be giant animals or god-like beings who thrashed the earth or oceans in to being in a fit of anger, love, fun, or some such verb of probably far from random selection. In any case, when creating art, we are creating a finite world: that is, one with edges. Artists usually call this the 'frame', but in fact some of them decided to make a point of using jars full of poo instead, so the frame became transparent ... which requires transparent things like glass, which are lenses and haven't been invented yet, so perhaps we're getting ahead of ourselves and shouldn't get so technical!
The point here is that in creating something as the output of our photographic process, we are in fact somewhat like these divine beings: verb-ing in to existence a finite milieu. As photographers shooting (and therefore as artists making) we take on those god-like qualities of creating and destroying worlds at our very whim. Some creation myths begin with a pure white brightness ("let there be light!"), others the bottomless black of an empty universe. Still others have complex and fleeting tonalities, like the churning of an ocean of milk. As photographers, we are concerned with all three of these as our raw material for creation.
From an evolutionary standpoint, let us suggest for a moment that in the beginning there were eyes. Not just floating in the void, mind you, but attached to bodies. If an eye - and, dragging it along kicking and screaming, the body it remained attached to - stayed still for a few moments, then sometimes things would move. Noticing this was beneficial to certain kinds of creatures, such as our own ancestors, as they could use this information to avoid predators (big scary sabre-toothed tigers) or to find food (colorful fruit falling from trees, for instance). Our brains, the most sophisticated by many measures on the earth today, spent millions of years evolving extremely well to efficiently process sophisticated images to detect both movement and objects of interest within a still frame. Back in those days, imagery was all about danger, food, and other serious business: the stuff of life that keeps you standing ... or gets you eaten. As it happens, our ancestors were particularly adept at using these powers, and eventually the sophisticated imagery of complex human vision emerged from the primordial soup. Incidentally, when we are born, scientists now know that our brains only see random sensory input, they don't have a presupposition that these-nerve-endings-over-here are to do with vision, and those-nerve-endings-over-there are to do with touch. It's all just random input, and in fact in recent years multiple adults have re-trained their brains to receive balance or sight from their tongues.
Though there was probably very little art in those early times, our aesthetic senses had long since begun to evolve from innate responses to natural stimuli such as commanding views (safety), darkness (danger), light (warmth), and so on. These associations would carry forward in to art as we began to discover ways to record our perceptions of the world: in physical art such as cave paintings, through our sophisticated and relatively unique command of language, and through social modes of communication such as dance and ritual.
Sitting still and going far
Still later, yet far before cameras appeared, humans used these powers of observation to realise fundamental principles of light. They knew, for example, that observation of the movement of shadows cast by standing objects over time could be reliably predicted and even associated with the time of day: if you stood at the end of the valley when the shadows had grown long, then you had better run back to the cave or face the evening hunt of the local tigers! This led, as humans began slowly to ponder such mysteries to good effect, to various sorts of technological innovations: chiefly calendrical and architectural, but also mathematic, for the line of a shadow is pure and its relationship to the source intrinsic.
When copying something, or the image of something, it's usually impossible to do so accurately. This is true fundamentally for the process of depicting our three-dimensional world (four if you count time!) on any two dimensional artwork: including approximately two dimensional cave walls, modern photographs, and early pictures. There are many reasons for this, but perspective an important factor: our brains cannot perceive depth and therefore anything approaching realism on a flat piece of paper unless given other clues. The first such clue was size, or perspective.
The Grotte Chauvet cave in France includes some of the world's earliest known cave painting, estimated at about 32,000 years old. It is unclear whether these paintings specifically included the device of relative scale, however much of the global body of neolithic art did, ie. the artists sized objects and characters hierarchically according to their spiritual or thematic importance, not their distance from the viewer. It could be argued that theirs was a symbolic perspective, rather than a physical one.
The second such clue was overlapping to suggest relative depth. This was certainly well in use by around the beginning of the common era, with global examples plentiful, for instance in early ancient Egyptian art and Chinese Han Dynasty tombs.
The third such clue was tone. It took humans a great deal of time to comprehend fully the expressiveness of tone for the illusion of depth. Given the relative tonal limitations of naturally occurring rock outcrops and other early media such as pottery, it is perhaps not surprising to realise that the exploration of tone perhaps naturally almost co-incided with the development of that most powerful of mediums: paper! Paper appeared in China at least as early as the early second century BC. According to textual evidence, by the fifth century some of the earliest artwork exploring tones - the layered ink work of the Chinese 山水画 or "mountain and water painting" - had already developed to prominence.
Probably at the same time as the above developments, investigation in to visual perspective began, for instance around the fifth century BC in Greece where the philosophers Anaxagoras and Democritus worked out geometric theories of perspective. Euclid's Optics, a mathematical treatment of perspective, soon followed in around 300 BC.
Then man said...
"Let there be lenses!" Eventually, a distant ancestor of ours had the bright idea of ending all this enjoyable evolutionary fun by discovering naturally occurring crystals that were capable of acting as lenses. Modern evidence of ancient lenses is partial, with some direct finds and some extremely fine workmanship that is held as evidence of lens-work.
In the former category, as recently as the last few years, concepts of ancient navigation in the north Atlantic are being reevaluated following the discovery of formerly near-mythical convex-lens sunstones made from a transparent calcite crystal known as 'Iceland spar' that allowed sailors to determine the direction of the sun even on very cloudy days, and after nightfall in northern latitudes. While the 16th century shipwreck it was found on is fairly late, it is thought to have been an established device by this era, having been referenced in 12th century literature as existing at least as early as the 10th century. The story is compounded by the Visby lenses, a collection of lens-shaped manufactured objects made of rock crystal (quartz) found in several Viking graves on the island of Gotland, Sweden, and dating from the 11th or 12th century. But that's nothing! An 1858 excavation at Niniveh in Babylon also unearthed an ancient Assyrian lens, now known as the Nimrud lens or Layard lens, dating from 750–710 BC, now held in the British Museum and thought to be the oldest in the world.
In the latter category, extremely fine workmanship of a kind considered unattainable with the naked eye (less than 0.1mm) qualifies a 1.3mm wide ivory carving from Abydos, Egypt, recently discovered by German archaeologist Gunter Dreyer that dates from 3300 BC. Other later but still early objects such as the Isopata gold ring from Crete, dated 15th century BC and with workmanship below 0.5mm and approaching 0.1mm and a jasper carving from second century Rome with 0.1-0.2mm details challenge alternate explanation.
Later, a friendly Italian fellow known as Giambattista Della Porta said let there be lenses on cameras! .. or words roughly to that effect. (He was in fact a failed dramatist with a flair for science, blessed with proximity to Venice, a major contemporary center of glass work, who also produced written works on refraction - the bending of light that is the primary science behind basic lens design.)
The coming of the Camera obscura
The lensless camera, or camera obscura is essentially an opaque box or room with a hole in it. The first surviving mention of some of the principles behind the pinhole camera or camera obscura belongs to 墨子 (Mozi; 470-390 BCE), a Chinese philosopher and the founder of Mohism. Mozi correctly asserted that the image in a camera obscura is flipped upside down because light travels in straight lines from its source. His disciples developed this into a minor theory of optics.
In the western world, the camera has been in use in principle since the Renaissance. It was known as the camera obscura, Latin for 'dark chamber', and consisted of a darkened room with a pinhole in the wall facing the subject, which would be outside the room. An inverted image would fall on the opposite wall, which would then be traced manually.
What is a camera?
At its most basic, a camera is a system for projecting light onto a surface, typically but not exclusively for the purposes of recording the image. This broadest definition includes microsocopes, camera obscura, digital cameras, video cameras (previously known as cine cameras), cell phone cameras and other such devices that are related to conventional cameras but do not necessarily include all of the same features.
Various dictionaries offer a surprising variety of generic but dated definititions for 'camera', most of which predate digital cameras and exclude both lensless devices (pinhole/camera obscura) and video cameras. Here are some examples:
- Collins English Dictionary (United Kingdom; 2012): an optical device consisting of a lens system set in a light-proof construction inside which a light-sensitive film or plate can be positioned
- Macquarie Dictionary (Australia; 2014): a photographic apparatus in which a sensitive plate or film is exposed, the image being formed by means of a lens.
The three basic components of a camera are:
- A directional light source, which, generally having bounced off the subject, can be said to contain an image of that subject.
- A device to record or display the image, which is generally either traditional film or a digital sensor, but can also be various alternative forms of chemical recording surface, glass plates, or similar flat surfaces with the objective of recording or displaying an image.
- A shutter or alternative means of beginning and ending the exposure of the recording device to the light-containing image
In general, the light that contains the image has to be segregated from (or in some cases, merely much stronger than) any other light present, or the image will not form (too much light will result in a purely white image, or 'overexposure'). To aid in the control of light, which is the primary process in photography, cameras are therefore generally designed as closed boxes that do not permit light from entering except from one direction, that of the subject. Such a design allows the camera to be pointed towards a subject, and during the exposure only light from that subject (ie. that which contains an image of the subject) will flow in to the camera, thus resulting in a clean image.
Some examples of cameras
Let's look at some examples.
- In the case of a 'pinhole camera', one of the simplest types of cameras that it is possible to make, the direction of the image is controlled simply by punching a small hole in the camera box which functions to project an inverted image of the subject on to the surface (eg. recording device) inside.
- In so-called 'sun printing', the sun is used as a light source and neither a hole nor a lens is used, indeed the camera does not even exist! Instead, items are placed across the recording device (most frequently using a cheap, outdated chemical process like cyanotype) to result in their outlines being recorded.
- In the case of the 'view camera' category, which evolved from the 19th century and is still used today, the image is generally captured through a lens (though pinholes can be used), and various types of exposure control are available.
- In the case of a modern SLR (single lens reflex) or DSLR (digital SLR) camera, the image is almost always a captured through a glass lens, using a precise shutter to control the length of exposure.
|Pinhole camera||Sun printing||View camera||Modern DSLR|
|Directional light source||Pinhole||Sun||High quality lens||High quality lens|
|Shutter||None (manual and approximate)||None (manual and approximate)||Sometimes||Yes (precise)|
|Aperture control||None||None||Usually||Precise mechanical aperture|
|Recording device||Any.||Chemicals||Commercial film or digital sensor.||Digital sensor.|
|Nature of image||Inverted||Silhouette||Inverted||Normal|
Today, when we discuss cameras we are almost always discussing modern cameras, those incorporating an opaque camera body, precise shutter speed and aperture control, and a proper lens.
The camera body
The purpose of a camera is to project light onto a surface that will record an image. Most cameras have the same basic controls and these controls affect how the image is recorded. The three basic controls are:
- Shutter speed: The amount of time that light will be allowed to pass through the lens during the exposure (ie. between the beginning and the end of the photograph). The longer the shutter is open, the brighter an image will become, however the image will also be more sensitive to motion blur as a result of movement in the camera or the subject it is capturing. Sports or action photography therefore depends upon fast shutter speeds (ie. shorter exposures), whereas careful and slow photography of relatively dark or still subjects (mountains, stars in the sky, etc.) generally depends upon slower shutter speeds.
- Aperture: The size of the (usually roughly circular) opening behind the lens. A larger aperture (or opening) will allow more light to pass through the lens than a smaller one. A larger opening will create a brighter image. Apertures are measured in 'f-stops', which are written f/number. Note that these numbers are 'backwards': somewhat confusingly, smaller numbers (such as f/0.95) mean bigger openings and/or more light entering the camera, whereas larger numbers (such as f/6.3) mean smaller openings and/or less light entering the camera.
- Sensitivity (often when expressed casually, ISO, which actually refers to the ISO 5800 standards documents originally published for film speed by the International Organization for Standardization): In any event, the sensitivity of the film or digital sensor to light. In traditional film cameras, you had to swap film to change this factor because it was a property of the type of film being used. In modern digital cameras, the ISO rating describes film-speed equivalency and is almost always possible to change in the camera, either manually or automatically. The scale is airthmetic, which means that a film with a rating of ISO 800, for example, will be eight times more sensitive to light than one of ISO 100. A higher ISO is useful in low light environments, however increasing the ISO will affect the quality of the image: in film the images become grainy, and in digital the image becomes noisier, with more undesirable speckles. Some of these noise articles can be removed after the fact, however, and low light performance is an area in which digital sensors have been making rapid improvements in recent years.
Changing any of the settings will affect how the image looks and will be discussed further later. For now let's examine different cameras and where these controls can be found.
Types of cameras
The following terms have been historically used to describe various types of cameras. These terms are not exclusive (for example, you can have a Single lens reflex or twin lens reflex pinhole camera), nor are they necessarily the only terms around. They are included here for reference purposes.
By lens type
The pinhole camera is relatively rare today, but is enjoying a resurgence of casual interest due to its simplicity. It is one of the simplest camera designs possible and has three major components: a light-proof box, a light sensitive material (such as a traditional analog film, or a digital sensor) and opposite the material a hole that light passes through carrying the external image. There is no lens; the aperture is created by punching a small hole opposite where the film is mounted and is very small; and the 'shutter' in more advanced cameras is emulated manually by uncovering and covering the opening. Despite its simplicity, it still has many enthusiasts because of the unique pictures it creates and the imaginative ways of turning ordinary objects into pinhole cameras.
Analog pinhole cameras are very easy to make from scratch for exposing traditional film: the principle is identical to the pioneering camera obscura experiment. Typically, a prefabricated, light-sealed container like a biscuit tin or a match-box can be used. Most digital cameras with changeable lenses can be converted in to pinhole cameras by replacing the lens with a sheet of opaque material with a hole punched in it.
Note that a method exists for calculating the optimum pinhole size: too small or too large and the image will lack definition.
By focal method
Focus is fundamental to photography, a fact that has determined the development of the different broad types of camera. Focus is dependent upon a number of relationships, distance of the subject from the camera being the most important. A rangefinder is just that - a device to find the range of a given subject from the camera, that the camera, in turn, can be focused. Rangefinder cameras fall into two separate sub categories, those in which the rangefinder is coupled to the focusing mechanism of the camera (coupled rangefinder cameras) and those in which the rangefinder is used to determine the distance only - which is then transferred to the lens manually, clearly a less convenient, but cheaper, option.
By method of optical projection
Twin lens reflex
The exact origins of the twin lens reflex (TLR) camera are obscure. Double-lens cameras were around from about 1870, when someone realised that having a second viewing lens alongside the taking lens meant that one could focus without having to keep swapping a ground glass screen for the plate afterwards, reducing the time delay in actually taking the shot.
Where the TLR came into its own was with the idea of using a reflex mirror to allow viewing from above, thus allowing the camera to be held much more steadily if handheld. The same principle of course applied to the single lens reflex, but early SLRs caused delays and inconvenience through the need to move the mirror out of the focal plane to allow light to the plate behind it. When this process was automated, the movement of the mirror could cause shake in the camera and blur the shot.
One of the earliest documented TLRs was made by the firm of R & J Beck of Cornhill, London in 1880 for Mr G M Whipple, a scientist and Superintendent of the Royal Observatory at Kew. It seems the design concept was his - to build a mirror reflex camera for cloud photography. The aim was to have a camera with lenses pointing upwards, but also to be able to compose the picture whilst looking horizontally. It seems this camera also used geared linking to synchronise the lenses, thus having many of the features of later mass-marketed TLRs .
There were a number of other types of TLR marketed between about 1890 and 1910, but these were gradually overtaken as more effective SLRs became available and cured the problem of parallax which bedevilled the TLR. The ability to see and compose the subject exactly in the taking lens outweighed the disadvantage of the moving mirror as SLR mechanisms improved.
Single lens reflex
As already discussed, focus is fundamental to photography, both in terms of what is and what is not in focus. A rangefinder camera, which allows one to determine the focusing distance, determines what should be in focus, but without actually demonstrating the degree. The TLR (Twin-Lens Reflex camera) goes one step further, by using a second viewing lens.
However, it is the SLR (Single Lens Reflex camera) that solves the problem fully. In this type of camera a mirror intercepts the light that passes through the lens and projects it onto a ground glass screen where it forms an erect (upright) but mirrored image. Now the photographer is truly viewing through the lens and able to accurately determine both the focus and depth of field. When the photograph is ready to be taken the mirror is retracted allowing the light to pass directly to the film, when the shutter is opened. The earliest models required the mirror to be retracted manually (this disappeared with the Speed Reflex in the mid-1920s), did not have the familiar prism of today, and demanded the viewer to inspect the image through a leather tlunnel to the ground glass screen. Another common feature of SLRs necessitated by their construction was the need for the light to pass through the lens to the reflex mirror unhindered. This lead to the focal plane shutter, where the mechanism is placed just in front of the film.
This is how most people perceive the SLR with the distinctive prism housing on top that first appeared on a Contax camera in 1948.
The prism serves to reflect and flip the mirrored image from the ground glass screen to the viewfinder, resulting in an erect and true image which is bright and often magnified by the viewfinder optics. The use of 35mm film allows these cameras to be relatively compact which removed one of the SLRs drawbacks. With the shutter positioned just ahead of the film within the camera's body, it is possible to change lenses without exposing the film, making the design very flexible. The principal shortcoming is that the focal plane shutter uses a variable gap to vary the shutter speed and that only a longish exposure time will synchronise with flash.
The view camera is of either a monorail design or what is called a flat bed or field camera. The flat bed being an older design and dating back to the middle of the 19th century. In both designs a flexible bellows separates the lens and film. The lens is affixed to a front standard and the film positioned in the rear standard. Both front and rear standards can move horizontally along the rail of a monorail or on tracks in the bed in the case of the flatbed design. In most designs the front and rear standards are equipped to pivot in both the x and y axis independent of each other. These are called "swings" and "tilts". There is usually some allowance for the rise and fall of both front and rear standards along the vertical plane. All of these movements allows for great flexibility in the control of the image.
There are many types of photographic lenses, the most common categories of which are outlined below. (For a more technical treatment of the subject you may wish to refer to Wikibook Optics.)
A so-called 'normal' lens bends light roughly the same way our eyes do, thus providing an image with the proper proportions. It has a focal length close to the diagonal measurement of the image frame. That is, with a standard 35mm format full frame camera, the image on the film or digital image sensor measures 24x36mm. The diagonal measures 43mm (sqrt(362+242)). The closest lens most manufacturers produce is the 50mm lens. Cameras with formats other than 35mm have 'normal' lenses with different focal lengths — longer for larger formats, and shorter for smaller formats.
- 35mm - Nikon Nikkor 50mm f/1.4, Canon EF 50mm f/1.4, Pentax smc P-FA 50mm f/1.4, Minolta AF 50mm f/1.4, et al
- 645 - Pentax smcp-FA 645 75mm F2.8, et al
- 6x7 - Pentax smcp 67 105mm F2.4, et al
- APS-C - Sigma 30mm f/1.4
You can compare lens focal lengths across various film formats using this external chart.
Wide-angle lenses have a larger field of view than normal lenses. In other words, they capture more of the scene in front of the camera by capturing more of the periphery. However, as the size of the film or sensor in the camera is still the same, the wider scene appears on the film or sensor as being slightly distorted: the bigger scene is "squeezed" onto the same area of film or sensor, so the typical effect is that each object is smaller (and therefore looks farther away) because the image now "includes" more objects. With each object smaller, the typical effect is that objects seem farther away. What you see in the passenger side wing mirrors in cars is the same. Those mirrors give a wide-angle effect and allows you to see more of the scene behind the car by making each object smaller, hence the common warning printed there: "Objects in mirror are closer than they appear."
There are various wide-angle lenses, measured by the focal length. The "normal" lens for a 35mm camera is about 50mm focal length, and a wide angle lens has a shorter focal length, such as 35mm or 28mm. The shorter the focal length, the greater the perspective distortion. At the extreme end, there are wide-angle lenses with a focal length of 10mm or so using a "fish eye" projection: up to a 180 degree field of vision can be captured. However, the final photograph looks highly distorted and looks like a photograph of the scene as if reflected on a silvered ball. It may be that the name of this type of lens comes from what one imagines a fish sees under water, or that the image is distorted around a central point much like what a fish eye looks like.
A long focus lens is any fixed focal length lens that is longer than a normal lens (focal length is longer than the diagonal measure of the film or sensor). This includes the common sub-type, the telephoto lens, which uses special optics to compress the length of the lens.
These lenses bring the subject in by magnifiying the subject and isolating it in the viewfinder. Lenses of this type are very useful for sports and wildlife photography for their ability to isolate a subject. However, these lenses have a drawback in that they typically are poor for low light use. Most long-focus lenses have a maximum aperture of only f/4, thus not permitting much light to reach the film and causing the use of slow shutter speeds to get correct exposure. In doing so, the photographer runs the risk of blurring the image due to his or her own movement.
One thing to bear in mind, try not to handhold your camera while using a shutter speed lower than that of the focal length of the lens being employed. This will help to assure sharper images. Using a sturdy tripod and a remote release will help a lot in low light photography.
Zoom lenses are multi-focal length lenses. A fixed lens (or 'prime' lens) has one focal length descriptor (e.g. 55mm). Zoom lenses cover a range of focal lengths (e.g. 35-105mm). A zoom lens can thus be adjusted to act as a wide angle lens all the way through to a telephoto lens.
The disadvantage of zoom lenses is that the focal complexity and number of lens elements required to achieve a range of focal lengths is much greater than for prime lenses. This is becoming less of an issue as lens manufacturers achieve higher standards in lens production. This has allowed zoom lenses to produce pictures of a quality comparable to that achieved by lenses with fixed focal length. Another disadvantage of zoom lenses is that the maximum aperture (the speed) of the lens is usually lower. This makes inexpensive zoom lenses hard to use in low-light conditions without a flash.
Macro lenses have the capability to focus objects that are very close to camera without distorting the image. Generally any lens that has a magnification of 1:1 (life size) or better at its minimum focusing distance is referred to as a macro lens.
Perspective-control (PC) or Tilt/Shift (TS)
When the film plane is not parallel to the surface of a subject, the subject is rendered with converging lines (lines parallel in reality are rendered converging). Typical example is when the camera is tilted upwards to photograph a building. The effect of converging lines is often unwanted and can be avoided by using a perspective control (PC) lens. It provides a function that is usually only available in view cameras: the lens can be shifted out of the optical axis (in the above example: upwards) and thus the recording media can be positioned parallel to the subject (the camera ponits orthogonally towards the building) and the subject is rendered undistorted.
Shift lenses are mechanically and optically more complex than ordinary lenses, don't provide autofocus and are comparatively expensive. They are often wide angle lenses and in this case frequently used in architecture photography. Longer lenses are often used in product or advertising type studio photography.
A catadioptric, or mirror lens, makes use of mirrors to reflect light back and forth though the glass elements with the second convex mirror element acting as a negative lens, further extending the light cone. The result is a dramatic decrease in the length of a lens whilst still maintaining a larger focal length. Mirror lenses create tell-tale doughnut shaped highlights when a light is located in an area of the photograph that is out of focus.
A lens that renders the image a little softer (i.e. less sharp). This is sometimes used in portrait photography to conceal minor defects in the skin of the person. To suit this purpose soft focus lenses usually have focal lengths around 80-100mm (fFor 35mm cameras) most popular for portrait work.
The term 'fisheye' was coined in 1906 by American physicist and inventor Robert W. Wood based on how a fish would see an ultra-wide hemispherical view from beneath the water (a phenomenon known as Snell's window). Their first practical use was in the 1920s for use in meteorology to study cloud formation giving them the name "whole-sky lenses". The angle of view of a fisheye lens is usually between 100 and 180 degrees while the focal lengths depend on the film format they are designed for.
Mass-produced fisheye lenses for photography first appeared in the early 1960s and are generally used for their unique, distorted appearance. For the popular 35 mm film format, typical focal lengths of fisheye lenses are between 8 mm and 10 mm for circular images, and 15–16 mm for full-frame images. For digital cameras using smaller electronic imagers such as 1/4" and 1/3" format CCD or CMOS sensors, the focal length of "miniature" fisheye lenses can be as short as 1 to 2mm.
- That was the Dadaists.
- That means 'world' in French, a fact which is primarily useful to pretend everyone else knows at parties.
- See The Brain That Changes Itself, a great book on these recent developments in science.
- The Australian aboriginal people, whose culture still exists, have paintings made 60,000 and 40,000 years ago.
- Stated differently, they did not use foreshortening.
- Physical fragments dated 179-41 BC have been recovered.
- No pun intended.
- camera. Collins English Dictionary - Complete & Unabridged 2012 Digital Edition.
- camera. Macquarie Dictionary, Macmillan Publishers Group Australia, 2014.
- Or around the subject, if recording a silhouette!
- We should really note that there are different types of light, which have different properties, and different recording devices have differing and unequal degrees of sensitivity to these various wavelengths of the continuous spectrum of light waves, however to keep things simple we'll save this pedantry for a footnote.
- In former times, it was possible to accidentally double-expose images (typically by forgetting to 'wind on' the film after a photograph), thus combining images of multiple subjects in to a single image for artistic purposes.
- Such as the cyanotype process.
- Even plastic lenses in toy cameras, cheap webcams or mobile phones are superior to lens-less pinhole cameras in terms of the focus and overall quality they can produce.
- Lenses, which are a swappable component on many cameras, are generally described using their minimum f/ rating (ie. the maximum amount of light which they permit). Lenses with small numbers (such as f/1.0) are described as fast, whereas lenses with big numbers (such as f/6.3) are described as slow.