Select your language
  • Deutsch

    Sämtliche Inhalte auf der CPN-Website sind auf Englisch verfügbar. Einige Inhalte, wie z. B. Produktbeschreibungen, aktuelle Produkteinführungen und einige technische Artikel, sind ebenfalls auf Deutsch, Spanisch, Französisch, Italienisch und Niederländisch erhältlich. Wählen Sie in der Liste oben Ihre Sprache aus, damit sämtliche darin verfügbaren Inhalte automatisch entsprechend Ihrer Wahl dargestellt werden. Ansonsten wird als Standardsprache Englisch verwendet.

  • English

    All content published on the CPN website is available in English. Some content – such as product descriptions, recent product launches and some technical articles – is also available in German, Spanish, French, Italian and Dutch. Choose your language from the list above and all content that is available in your language will automatically be displayed in your language, otherwise the default language will be English.

  • Español

    Todo el contenido publicado en la página web de CPN está disponible en inglés. Parte del contenido –como descripciones de producto, lanzamientos recientes de productos y algunos artículos técnicos– también están disponibles en alemán, español, francés, italiano e holandés. Elija su idioma en la lista anterior y todo el contenido que esté disponible en su idioma aparecerá automáticamente en ese idioma, o , si no, en el idioma predeterminado que es el inglés.

  • Français

    Tout le contenu publié sur le site Web de CPN existe en anglais. Une partie du contenu (comme les descriptions de produit, les lancements récents de produit et certains articles techniques) est également publié en allemand, en espagnol, en français, en italien et en néerlandais. Choisissez la langue dans la liste ci-dessus, et tout le contenu offert dans votre langue s’affiche automatiquement ; par défaut, le reste s’affiche en anglais.

  • Italiano

    Tutti i contenuti pubblicati sul sito CPN sono disponibili in inglese. Alcuni contenuti come descrizioni di prodotto, lanci di prodotti recenti e alcuni articoli tecnici sono disponibili anche in tedesco, spagnolo, francese, italiano e olandese. Seleziona la lingua dall'elenco in alto e automaticamente si visualizzeranno tutti i contenuti disponibili in quella lingua; diversamente la lingua di default sarà l’inglese.

  • Nederlands

    Alle inhoud die op de CPN-website wordt gepubliceerd, is beschikbaar in het Engels. Bepaalde inhoud, zoals productbeschrijvingen, onlangs gelanceerde producten en sommige technische artikelen, zijn ook beschikbaar in het Duits, Spaans, Frans, Italiaans en Nederlands. Kies de taal uit bovenstaande lijst, waarna alle inhoud die beschikbaar is in de gewenste taal, automatisch in die taal wordt weergegeven. Anders is Engels de standaardtaal.

Technical

June 2007

It was on 17 February 1987 that Canon announced a “new dawn” in 35mm photography with the launch of the EOS 650 camera.

The EOS 650 was the first camera in the EOS range.
 

The EOS 650 was the first camera in the EOS range.

Today, it is difficult to appreciate just how much of a gamble this was for the company. The EOS 650 was not just another new camera – it was the launch of a system that effectively replaced everything that had gone before. It was not compatible with any previous lenses, and very few existing accessories could be used. Switching to an EOS camera required an investment in a completely new system.

Classical note

The name EOS is an abbreviation of Electro-Optical System. However, Canon was also making an allusion to Eos, goddess of the dawn in Greek mythology. She is probably better known by her Roman name of Aurora, which she lends to that luminous phenomenon, the Aurora Borealis, or Northern Lights.


Early autofocus

The FD35-70mm f/4 AF was Canon’s first autofocus lens for a single-lens reflex (SLR) camera. It fitted all models with an FD mount.
 

The FD35-70mm f/4 AF was Canon’s first autofocus lens for a single-lens reflex (SLR) camera. It fitted all models with an FD mount.

All EOS cameras offer autofocusing (AF) – the lens automatically focuses on the subject in a fraction of a second. But this was not Canon’s first venture into the area of autofocus with single-lens reflex (SLR) cameras. In May 1981 the company introduced the FD35-70mm f/4 AF lens. This used the FD mount common to Canon SLR cameras at the time. All the autofocus technology was built in, so the lens could be used with any camera with an FD mount. The lens was bulky and slow, but it was the only AF lens available for SLR cameras at the time, and it worked.

In 1985, Canon introduced the T80, its first autofocus SLR camera. This accepted not only the full range of non-autofocus FD mount lenses, but also a new range of autofocus AC lenses. However, only three different AC lenses were available and the camera was not a big success. It is best seen as a stop-gap model waiting for the introduction of the EOS system two years later.

The new mount

With the FD AF lens, and the T80, Canon had shown it was possible to add autofocusing within the FD lens mount system. So why did it introduce the new electro-focus (EF) lens mount for EOS cameras? Essentially because its forward-thinking designers realised that it needed a new mount to accommodate future technological possibilities.

The new lens mount for the EOS system replaced the mechanical linkages of the FD system with eight gold-plated electrical contacts.
 

The new lens mount for the EOS system replaced the mechanical linkages of the FD system with eight gold-plated electrical contacts.

Advances in electronics meant that mechanical linkages were no longer needed between the camera and the lens. The EF mount uses eight gold-plated contacts to transfer data quickly and accurately. Up to a dozen different pieces of information are exchanged each time a photograph is taken.

Also, the diameter of the mount is a little wider than that of the earlier FD mount allowing ultra-wide aperture lenses to be designed for the system.

The fact that a lens mount introduced in 1987 was more than able to cope with the demands of the latest digital camera is testament to the vision of the designers. Without exception, every EF lens produced is compatible with every EOS model.

Autofocus actuators

The arc-form drive (AFD) is a conventional motor shaped to fit around the inside of a lens barrel.
 

The arc-form drive (AFD) is a conventional motor shaped to fit around the inside of a lens barrel.

One problem with autofocus lenses was that the motor needed to move the lens elements. At the time, motors were fairly bulky. Some manufacturers solved the problem by positioning the lens motor inside the camera body, linking it mechanically to the lens. This was not ideal, as different lenses need different degrees of movement for focusing from a few feet to infinity. A motor in each lens was the answer, but appeared to be inconvenient and expensive.

Canon overcame the problem with a technological breakthrough. Rather than trying to fit the lens to a motor, they designed motors to fit the shape of the lens. The arc-form drive (AFD) actuator (motor) sits snugly round the lens barrel. Each different lens has its own AFD designed to suit the individual characteristics of the focusing system.

Every EF lens contains an electro-magnetic diaphragm (EMD) to control the opening and closing of the lens aperture.
 

Every EF lens contains an electro-magnetic diaphragm (EMD) to control the opening and closing of the lens aperture.

At the same time, Canon introduced the now-familiar ultrasonic motor (USM) for some of the lenses. This employs ceramic piezoelectric elements that vibrate and generate a wave pattern to create movement (rather like a coin moving across the flat surface of a vibrating washing machine). Ultrasonic motors are very fast, near-silent, and their ring shape is ideal for fitting into lens barrels.

Both types of motor are very efficient because they can be fitted right next to the focusing mechanism they drive.

Every EF lens also has a second motor, used to operate the lens aperture. Motor control of the aperture is much more accurate than the mechanical lever operation of previous lenses.

Side by side

Although the EOS 650 marked a revolution in camera design, its main market was the amateur rather than the professional photographer. The EOS 620, which was launched a few months later, had a higher specification, but was still not a professional model.

The first professional model in the range – the EOS-1.
 

The first professional model in the range – the EOS-1.

At this time, many professionals were using the Canon New F-1, a well-established camera taking FD lenses. Also around was the award-winning T90. Although this was not directly aimed at the professional market, the extensive, high-end specification made it the first choice as a back-up camera for many professionals.

The first professional autofocus model was the EOS-1, introduced in September 1989. The autofocusing sensor was four times more sensitive than the sensor used in the EOS 650, and it offered spot metering. The body was more rugged than those of the consumer models, and it was designed for the wear and tear of daily use.

For several years the EOS-1 and New F-1 cameras were sold side by side. Many professionals had invested thousands of pounds in FD lenses and accessories, and were reluctant to start all over with a new camera system. A few felt that autofocusing, while fine for the consumer, removed control and creativity from the professional. However, the results from the EOS-1 spoke for themselves, and the migration from FD to EF lenses continued. Eventually, the New F-1 was discontinued, followed some time later by the range of FD lenses. The switch to EOS was complete.

Lens development

When the EOS 650 was introduced in 1987 there were just six EF lenses available – ranging from the 15mm f/2.8 Fisheye to the 70-210mm f/4. Now there are well over 100 lenses in the range, both current and discontinued.

The history of EF lenses is one of innovation. It includes one of the widest aperture lenses ever made for a 35mm SLR camera, the EF50mm f/1.0L (September 1989), and one of the longest focal length lenses, the EF1200mm f/5.6L USM (July 1993).

L-series lenses are distinguished by a bright red ring near the front of the barrel.
 

L-series lenses are distinguished by a bright red ring near the front of the barrel.

The L-series range of EF lenses are designed for professional use and usually feature wide apertures. To maintain optical performance at these wide apertures, Canon uses fluorite crystal elements in place of optical glass to help reduce chromatic aberrations. In nature, fluorite only grows very small crystals. These were used back in the 1800s to produce small lenses for microscopes. Unfortunately, these crystals are too small for photographic lenses, so Canon devised a method of growing synthetic fluorite crystals in larger sizes. Engineers then had to develop new techniques for grinding the fragile crystals into lenses. It takes about four times longer to grind a fluorite element than a glass element – one of the reasons for the increased cost of an ‘L’ lens.

The first Canon lens to contain a fluorite element was the FL-F300mm f/5.6, produced in 1969. Fluorite elements are now found in several L-series super-telephoto lenses.

Lenses with fluorite elements are expensive, so Canon has done a lot of research into improving lens performance using different types of optical glass. Ultra-low dispersion (UD) glass has similar properties to fluorite in that it features a low refractive index and low dispersion. Although not quite as good as fluorite crystals, its performance is significantly better than that of ordinary optical glass. With UD glass elements, Canon has been able to manufacture a range of lenses with higher performance at lower cost.

In several L-series lenses, both fluorite and UD elements have been combined to produce optimum results. This search for enhanced lens performance continues today. Some digital cameras now outperform film in terms of resolution and need improved lenses to make the most of their capabilities.

Another optical technology pioneered by Canon was the aspherical lens. In the early days, all lens elements were spherical the easiest shape to produce. Unfortunately, a spherical lens element cannot make parallel rays of light all focus on one point. This creates an effect called spherical aberration. Canon designers discovered that an aspherical lens reduced or even eliminated this aberration. The degree of asphericity was so small that special manufacturing processes had to be developed to stay within the 0.1 tolerance required. Today, if the degree of asphericity is even 0.02 microns away from ideal the element is rejected.

DO elements

A diffractive optical (DO) lens element showing the concentric circles.
 

A diffractive optical (DO) lens element showing the concentric circles.

Canon also developed a technology that combines the characteristics of both fluorite and aspherical elements. It is called a Multi-layer Diffractive Optical element, or DO for short.

DO elements use a diffraction grating. In general terms, a diffraction grating is a sheet of clear glass or plastic engraved with fine, parallel grooves. The grating developed by Canon has equally-spaced concentric grooves. The grating is much thinner than a normal optical glass element. Like a glass element, a diffraction grating alters the path of light rays.

The EF400mm f/4 DO IS USM lens (top) is shorter than the EF400mm f/4 lens.
 

The EF400mm f/4 DO IS USM lens (top) is shorter than the EF400mm f/4 lens.

Diffractive elements had not previously been used in camera lenses because they tended to create superfluous diffracted light resulting in flare. Canon resolved this problem by combining two diffractive elements with opposing gratings. One of the advantages of DO elements is that telephoto lenses can be designed with a shorter physical length.

Image stabilisation

One major technology developed especially for EF lenses was image stabilisation (IS). It helps to reduce the effects of camera shake.

The image stabiliser unit detects movement of the lens.
 

The image stabiliser unit detects movement of the lens.

One way to eliminate camera shake is to fix the camera to a stable support, such as a tripod. However, it is not always convenient to carry or use a tripod. Canon has taken a lateral approach. Instead of keeping the camera steady, the IS lens introduces an opposing movement. It aims to keep the image steady on the film or sensor despite the movement of the camera.

When the camera is static, the rays of light pass through the lens and form an image on the film or digital sensor (top). When the camera moves, the rays of light from the subject are bent relative to the optical axis and the image shifts slightly on the film or digital sensor (centre). With an image stabiliser lens, the gyro sensors detect the camera movement and pass the data to a microcomputer in the lens. This instructs a special group of lens elements to move at right angles to the lens axis. The amount and direction of this movement is just enough to counteract the amount and direction of the camera shake. The result is that the rays of light passing through the lens are adjusted so that the image does not move relative to the film or digital sensor (bottom).

Camera shake is detected by two gyro sensors in the lens one for yaw and one for pitch. The sensors detect both the angle and speed of the movement. This data is used to control the movement of a floating element in the lens. This moves at right angles to the lens axis to keep the image steady. There is no reduction in the optical performance of the lens.

EF400mm f/2.8L IS USM
 

EF400mm f/2.8L IS USM

Camera progress

EOS cameras themselves have also provided a rich history of innovative technology. Just two years after the EOS 650 and 620 launched the system, Canon brought out the EOS 600 (April 1989). This is significant because it introduced three features that are still found in the latest models: PIC modes, predictive focusing and custom functions.

Program Image Control (PIC) is aimed at the consumer market and has never found its way onto a professional model. By selecting a shooting mode based on the type of subject, the camera will set a range of functions to suit that subject. Modes include landscape, portrait, sport and close-up.

Program Image Control (PIC) modes are called ‘image zone’ settings on more recent cameras such as the EOS 400D.
 

Program Image Control (PIC) modes are called ‘image zone’ settings on more recent cameras such as the EOS 400D.

Predictive focusing is now a standard feature of all EOS models. Its development was necessary because there is a slight delay between pressing the shutter button and the shutter opening. This is known as the shutter time lag. In this brief moment measured in milliseconds a fast-moving subject can cover a significant distance. If the lens focus is based on the subject distance at the moment the shutter button is pressed, the subject could be out of focus when the shutter opens. Predictive focusing measures the speed and direction of the moving subject and sets the focus for the point where it determines the subject will be when the exposure is made.

Custom functions are available on film and digital cameras. This menu display is from the EOS 10D.
 

Custom functions are available on film and digital cameras. This menu display is from the EOS 10D.

Custom functions offer a method of controlling a wide range of features without adding to the buttons and switches on the camera body. They are set using the LCD panel of film cameras or the menu system of digital cameras. This is slower than turning a dial to a setting, so custom functions tend to be used for features that you set once and then forget about, or only need to change occasionally. For example, on some professional models you can set the exposure values to change in 1 step, 1/2 step or 1/3 step increments.

Quieter cameras

The EOS 100 is one of Canon’s quietest EOS cameras thanks to the belt-drive system.
 

The EOS 100 is one of Canon’s quietest EOS cameras thanks to the belt-drive system.

A lot of the noise heard from the first EOS cameras was the sound of the film being automatically advanced after each exposure. A sprocket wheel engaged with the holes at the edge of 35mm film to pull it across the back of the camera.

The EOS 100 (March 1990) did away with the sprocket wheel, and much of the noise, by using a belt drive mechanism. The holes in the film were still needed, though – a small infrared device counted the holes as they passed over it. This provided an accurate measuring device to position the film for each new exposure.

Eye-control focus

One of the most significant cameras in the early years was the EOS 5 (November 1992). This camera was positioned between the professional and consumer models and appealed to both groups. It also introduced eye-control focus. This allowed you to focus on a subject simply by looking at it through the viewfinder. If the subject was in the top left corner of the frame, looking in this direction would bring it into focus.

Eye-control focus on the EOS 5 was limited to horizontal format images, but the EOS 3, 50E, 30 and 30V all provide eye-control focus in horizontal and vertical formats.

Multiple focus points

The earliest EOS models had a single focus point in the centre of the viewfinder frame. If your subject is off centre, you have to centre it in the frame before focusing, then lock the focus and recompose the image.

The EOS 10 (March 1990) introduced the concept of multipoint focusing, giving three focus points. In addition to the centre, there is a point to the left and one to the right. With autoselection set, the camera takes readings from all three points. Then, on the assumption that the main subject will be the item closest to the camera, it uses the point that indicates the shortest distance.

Since the EOS 10, focus points have multiplied. The EOS 3 (November 1998) introduced the 45-focus point array, which was then used in the EOS 1V (March 2000) and all the professional digital cameras. Like the EOS 5, the EOS 3 was designed to appeal to professional photographers and advanced enthusiasts.

Early EOS models had a single focus point (left). The EOS 10 introduced multi-point focusing with 3 points (centre). The EOS 3 and 1V, and the professional digital models, all have 45 focus points (right).

The EOS 1V is the most recent of the professional film cameras and has taken film photography just about as far as it can go. It offers an impressive specification in a water-resistant, dust-proof body.

The dawn of digital

The full-frame CMOS sensor used in the EOS-1Ds Mark II.
 

The full-frame CMOS sensor used in the EOS-1Ds Mark II.

Canon has been right at the forefront of digital photography. The first EOS digital camera was the DCS 1, introduced in 1995. This was a joint venture, with Canon supplying the body and Kodak providing the electronics. Three more digital models from the partnership followed until, in October 2000, Canon went it alone with the EOS D30.

The EOS D30 was the first to feature a CMOS sensor. Up to this time, CMOS sensors were regarded as inferior to CCD sensors. The main problem was that they created a lot of ‘noise’ (electrical background interference) that degraded digital images. However, CMOS sensors were less expensive to produce and used less battery power, making them more suited to EOS cameras. Canon engineers soon resolved the noise issue, and the quality of images from the D30 was as good as those from cameras using CCD sensors. CMOS sensors have been used in all subsequent EOS digital cameras, except the EOS-1D (December 2001).

Professional range

The DIGIC II, a powerful computer unit that processes the data captured by the CMOS sensor.
 

The DIGIC II, a powerful computer unit that processes the data captured by the CMOS sensor.

The EOS-1D was the first professional digital camera exclusively from Canon. It has a 4.15 megapixel sensor (low by today’s standard) but capable of a shooting speed of eight frames a second. This made it ideal for news and sports photographers, who welcomed the speed of digital imaging. With the camera, a laptop computer and a mobile phone, it became possible to transmit an image to a newspaper picture desk within minutes of making the exposure.

Many portrait and social photographers made the move to digital when Canon introduced the EOS-1Ds in November 2002. This offers an 11.1 megapixel sensor. However, it is not just the number of megapixels that is important. One of the reasons for the quality of images from Canon digital EOS cameras is the DIGIC processor. This is a powerful mini-computer inside the camera that takes the raw data from the sensor and converts it into a usable image file. The EOS-1D Mark II (April 2004) introduced the second-generation DIGIC II processor which provides images of even higher quality.

The EOS-1Ds Mark II (November 2004) introduced another leap in quality with its 16.7 megapixel sensor. Many photographers say this outperforms film, and some medium-format film photographers have switched because it meets all their needs.

Picture Style

Alongside the professional range of digital cameras is the consumer range. The EOS D30 was followed by the 6.3 megapixel EOS D60 and 10D, and the 8.2 megapixel EOS 20D and 30D. The entry-level range started with the EOS 300D, which was the first digital SLR available for under £1,000. It was followed by the EOS 350D and 400D. The 400D was the first EOS model to offer integrated sensor cleaning.

Between the professional and consumer models is the EOS 5D. This 12.8 megapixel camera was the first to feature Canon’s Picture Style system. These pre-sets simplify in-camera control over image quality, delivering JPEG images straight out of the camera without the need for additional processing. It is similar to choosing a film type. One pre-set gives strong vivid colour, another optimises colour balance and saturation for attractive skin tones, and a third provides stronger sharpening and deeper blues and greens for landscape photography. There are six different Picture Style pre-sets built into the camera, but additional styles can be downloaded from a Canon website.

Picture Style is also available on EOS cameras introduced since the 5D.

Sensor size

One of the features differentiating digital cameras is the physical size of the sensor. A sensor the size of a 35mm film frame (36 x 24mm) is very expensive to produce, so most models use an APS-C format (22.5 x 15mm). The smaller frame means that the angle-of-view of lenses is reduced, giving a telephoto effect compared to the same lens on a 35mm camera. To help alleviate this problem Canon introduced some wider-angle zoom lenses, such as the EF-S10-22mm f/3.5-4.5 USM.

The EF-S lenses only fit some of the consumer and entry-level models, such as the EOS 20D, 30D, 300D, and 400D. These cameras also accept the full range of EF-mount lenses.

The EOS-1D cameras use a slightly larger APS-H sensor (28.7 x 18.1mm). This gives less of the telephoto effect to lenses.

The EOS-1Ds models provide a full-frame (36 x 24mm) sensor, making the switch from 35mm film cameras more seamless. The EOS 5D also has a full-frame sensor.

The future of photography

Canon started producing cameras in 1937. It took over 60 years to reach the EOS 1V film camera. EOS digital cameras were born in 1997, and overtook the performance of film camera with the EOS 1Ds Mark II in 2004. In part, this short digital time span is because digital has been able to build on the expertise acquired in the design of film cameras. But it is also because the pace of technology is accelerating. Who knows where it will take photography in the coming years?