A History of Photography – Part Six

Canon Digital SLR Camera EOS 5D Mark II + EF24-105 Kit

Canon Digital SLR Camera EOS 5D Mark II + EF24-105 Kit

The Digital Age

The digital age of photography began in 1973. The invention of the integrated circuit chip in the late 1950s led to new electronic developments in the 1960s including the first Charge Coupled Device, or CCD chip. Each light-sensitive point on the chip changes the light intensity to an electric charge (in a capacitor). The charge is passed across the chip to an amplifier which creates a voltage. The CCD chip captures a frame at a time by coupling the charges and passed across the array. Fairchild Semiconductor    External link - opens new tab/page released the first large image-forming CCD [http://en.wikipedia.org/wiki/Charge-coupled_device ] chip of 100 rows and 100 columns in 1973 (black and white only). This was followed in 1975 by a colour CCD. Yet it was over a decade before Kodak invented the first megapixel sensor (one million pixels per sensor – 1986).

The charge coupling method was invented using minimal chip components. As integrated circuit chips improved the Complementary metal–oxide–semiconductor chip    External link - opens new tab/page (CMOS) was developed. Used for general integrated circuits the CMOS chip also provided a platform for imaging sensors.

The 1980s saw significant advances in circuit miniaturisation using the CMOS technology. CMOS chips allowed many components to be built into each pixel where light-stimulated charges were created. During the 1980s this saw each light sensitive area of the chips surface become not only a charge generator, but also its own mini-amplifier. These “Active Pixel Sensors” (APS) simplified the building of the chips – making them cheaper than older CCD technology.

Early 1990’s experiments with CMOS/APS technology showed advantages over CCD sensors. They compared well, but as the CMOS technology developed it proved to be more advantageous.

Advantages of the CMOS Vs. CCD

CMOS – cheaper to build

  • ‘Blooming effect’ minimised (strong light does not bleed-over electric charge to the next pixel)
  • Easy integration of light sensor and camera management into one chip
  • Lower power consumption
  • Faster image data processing

Disadvantages of the CMOS Vs. CCD

  • CMOS sensor captures data a row at a time from the sensor array. This may cause image skew (tilt depending on the direction of camera or subject is moving). Stationary objects will not skew, but something moving would be gradually captured at a row-a-time leading to some distortion as the movement changes between row captures. This does not happen when the whole frame is captured at once (CCD).
  • Relatively high noise levels compared to CCD requiring noise reduction technologies.

By the late 1990s CMOS technology had largely displaced the pure CCD chip. This was mainly because CMOS chips were easily developed into Active Pixel Sensors (APS) – a type of architecture for the image sensor chip. This should not be confused with the ‘Advanced Photo System Type-C’ sensor format used in many SLRS. An APS is a chip developed for a specific job, like imaging and camera management. Other application specific chips might be built for running a car, or being the processor in a desk-top computer. These types are not interchangeable.

Application specific chips enabled manufacturers to develop specialised chips for digital cameras. These systems captured the light intensity and colour. They also, processed the data, reduced noise, managed data storage and did camera management. Such chips is the Canon Digic system    External link - opens new tab/page processor range performs many powerful tasks beyond imaging. Its main function is the image exposure. It also provides ‘presets’ – selections the user can make. These allow use of sophisticated photography techniques with little photographic knowledge. The “night preset” sets the shot for very dark conditions and still produces a good image. The same applies to the portrait preset, landscape preset and so on. The camera program runs these ‘typical’ picture situations on behalf of the photographer. The latest version of the Digic processor can do some interesting new tasks. For example it can recognise 12 faces per picture and index them according to data given in advance. The user can upload pictures to social networking sites and the camera reports who is in the picture without user intervention. The Digic processor can also carry out ‘landscape recognition’ setting the camera up appropriately. These advances are computing tasks integrated into the imaging chip system.

Today most amateurs and professionals consider digital imaging systems in modern cameras to be at least equivalent to film in flexibility if not quality. It is fair to say that film still has a place in high end photography, particularly large format film. There are also some environmental conditions under which digital technology has not performed well – especially wet or extreme cold conditions. Late version high end professional range cameras have recently addressed this with improved environmental sealing.

Digital has surpassed film in many ways impacting the market to the extent that several big film companies have changed direction or gone out of business. Kodak recently filed for bankruptcy in the United States. While the brand may survive, it is unlikely that film production will ever start again. Digital has, for the moment at least, won the day.

It is difficult to see what the next stage in digital imaging will be. As with many industries, we may see a late resurgence of legacy-style systems in an unusual way. Many old recordings on records have moved onto CD. So, ‘film’ systems may in the future see a resurgence as an interesting hobby, supported by a renewed industry springing up. It is doubtful this will ever be more than a hobby market.

The human eye can see about 15 to 18 stops of light – a digital camera about 10 stops, film about 8 stops. This leads to loss of depth and contrast in digital (and film) images. High Dynamic Range photography (HDR) enhances this contrast-distinction by integrating images from different dynamic ranges into an image range similar to the eyes’ own range. While HDR images have a deeper tonal richness, the enhancement is artificial. Most HDR is detectable and artificial in appearance. However, greater sensor capability is developing. In time digital imaging will mimic the dynamic range of the eye, rendering dynamic ranges the eye cannot detect from real.

Stereoscopic three-dimensional photography is already advanced. However, the possibilities for still images are limited at present. So there are potential developments likely in that for the near future.

Innovation has always driven the passion in photography. So bring on the new inventions!

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.
See also: Editors ‘Bio’.

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