14 DAY TRIAL // By now, we know you know how analog pictures are tuned into digital ones and vice versa. However, printers and scanners can be seen as supporting hardware for what is the essential image capture device - the digital camera. I should have presented it first, but time isn't wasted as of yet. So, today we will explore the existent types of digital cameras and how these trendy pieces of hardware work.
Imprisoning reality A digital camera is the electronic device that captures and stores photographs digitally instead of using photographic film as old-fashioned cameras do. Present-day digital cameras are oftentimes multifunctional, being capable of recording sound and/or streaming video besides still photographs. As a matter of fact, digital cameras have become the device of choice, outselling their 35 mm film counterparts. Several types of digital cameras exist nowadays, but the most important are:
1. Live-Preview Digital cameras (or LPDs) are devices that use a conventionally generated digital image (live-preview) on an electronic display as its main mode of framing and previewing before taking the actual snapshot. Digital LPDs thus have a rear liquid crystal display for previewing and reviewing photographs. PC transfers are usually managed through the USB mass storage device class (because of this, digital cameras are recognized as smaller hard drives by the OS) or via the firewire connection, which is becoming more popular and supported among more digital cameras. All of these cameras use either a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor. These kinds of chips comprise a grid of phototransistors to sense the light intensities across the focus plane of the camera lens.
2. Compact digital cameras (or digicams) are characterized by great ease in operation and easy or even automated focusing; this design allows for limited motion picture capability. They usually feature small zooming ranges but this is compensated by an extended depth of field. This allows objects found at a considerable distance to be in focus, greatly accounting their ease of use. Digicams excel in landscape photography and typically save pictures only in JPEG file format.
3. Bridge digital cameras (or Prosumer) and dSLR (digital single lens reflex) cameras - form a general group of higher-end and high-end LPD cameras, sharing advanced features. However, the basic LPD design is to be found in these types of cameras, too. Traditionally, dSLRs use powerful CDDs coupled with interchangeable lenses and are considered the tool of choice for professional photographers, while bridge cameras have so far been prosumer or at best, semi-professional. However, Canon recently introduced a line of dSLRs that tend to blur the line between prosumer and high-end cameras. This new class of dSLRs can be described as consumer (compared to the higher classes of dSLRs), while the top bridge cameras remain prosumer (compared to compact LPDs). Official reviews which put the bridge and entry-level dSLRs side by side, reveal that they are on par. The term prosumer is derived from professional and consumer. Prosumer cameras tend to integrate a long or ultrazoom lens, in order to be a "do it all" model, but this is most of the times done at the cost of barrel distortion and pincushioning effects that downgrade the overall quality. Prosumer cameras are sometimes marketed as and confused with dSLR cameras since the bodies resemble each other. As stated before, the main difference is that the prosumer camera doesn't feature interchangeable lenses, dSLRs usually coming without any lens at all (the lenses are most of the times sold separately). In addition, prosumer cameras can usually take movies, record audio and the scene composition is done with either the liquid crystal display or the electronic viewfinder (EVF). They are typically more compact and lighter than dSLRs and a good thing is they can also save in RAW image format, previously implemented only in dSLRs.
Past achievements It is true that the concept of digitizing images on scanners predate the concept of making still pictures by digitizing signals from a light capturing array. Eugene F. Lally of the Jet Propulsion Laboratory published the first description of how to produce still photos in a digital domain. His descriptions presented the usage of mosaic photosensor. The purpose of this device was to provide onboard navigation information to astronauts during future missions to planets. The mosaic light-capturing array periodically recorded still photos of star and planet locations during transit. This concept also included camera design elements foreshadowing the completion of the first digital camera.
However, this development did not see any real application. Instead, first recorded attempt at building a digital camera was by Steve Sasson, an engineer at Eastman Kodak. It used the solid state CCD chips developed by Fairchild Semiconductor in 1973. The camera weighed almost 3.6 kg, recorded black and white images to cassette-tape media, had a resolution of 0.01 megapixel (10,000 pixels), and took 23 seconds to capture its first image in December of 1975. This prototype camera was never released on the consumer market.
The first analog camera marketed to consumers may have been the Canon RC-250 Xapshot back in 1988. Another noteworthy analog camera produced the same year was the Nikon QV-1000C, which sold only around 100 units. It recorded images in grey scale, and the quality in newspaper print was equal to film cameras. The camera body closely resembled a modern digital single-lens reflex camera.
True digital camera that recorded images as a computerized file became available with the introduction of the Fuji DS-1P model in 1988, which recorded to a 16 MB internal memory card that used a battery to keep the data in memory. This camera was available only in Japan. The first world-wide available digital camera was the 1991 Kodak DCS-100, the beginning of a long line of professional SLR cameras by Kodak that were based in part on film bodies produced by Nikon. It incorporated a 1.3 megapixel sensor and was priced at $13,000. The first consumer camera with a liquid crystal display on the back was the Casio QV-10 in 1995, and the first camera to use CompactFlash was the Kodak DC-25 in 1996. The first camera that offered the ability to record video clips may have been the Ricoh RDC-1 in 1995. In 1999 Nikon introduced the D1, a 2.74 megapixel camera that is considered to be the first digital SLR developed entirely by a major manufacturer, and at a cost of under $6,000. This camera also used Nikon F-mount lenses, which meant film photographers could use many of the same lenses they already owned from their film-based cameras.
The master plan While conventional cameras depend entirely on chemical and mechanical processes, practically requiring no electricity to operate them, all digital cameras have a built-in computer and record images electronically with the help of some power source. Present-day film-based approaches still provide better picture quality and digital cameras have not completely replaced conventional cameras. But, as digital imaging technology got more improved and was made even more user friendly, digital cameras have rapidly become more popular. Digital photographs have to be represented in a computer recognizable language made up of bits and bytes. Essentially, a digital image is just a long string of 1s and 0s that stand for all those pixels that collectively form the digital image.
Today, photographs can be taken using two main methods: - via a conventional film camera, then processing the film chemically and printing the result onto photographic paper. - via a digital camera, directly sampling the original light that bounces off the subject, immediately breaking that light pattern down into a series of pixel values. The digital camera is much like a conventional camera, as it has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a film-based media, it focuses it onto an image sensor that records light electronically. The integrated microcomputer then breaks this electronic information down into digital data.
Let us now concentrate a little more on the image sensors. Think of these sensors as a 2-D array of thousands or millions of minute solar cells that absorb light photons. Once the sensor converts the photons into electrons, it reads the value (accumulated charge) of each cell in the image. Now, there are two ways of reading these values, which can be seen in the two existing types of image sensors:
a) the CCD transports the charge across the chip and reads it at one corner of the array. An analog-to-digital converter (ADC) then turns each pixel's value into a digital value by measuring the amount of charge at each photosite and converting that measurement into binary form.
b) CMOS devices use several transistors at each pixel to amplify and move the charge using more traditional wires. The CMOS signal is digital, so it needs no ADC.
Here are some other differences between these two image sensor types: * CCD sensors create high-quality, low-noise images. CMOS sensors are generally more susceptible to noise. * Because each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip is lower. Many of the photons hit the transistors instead of the photodiode. * CMOS sensors traditionally consume little power. CCDs consume as much as 100 times more power than an equivalent CMOS sensor. * CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have more high quality pixels.
Final resolutions One of the defining features of the image sensor is the supported maximum resolution. This is the amount of detail that the camera can capture and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or "grainy."
Currently, the most common resolutions are: * 1216x912 - this is a "megapixel" image size featuring in fact 1,109,000 total pixels. * 1600x1200 - almost 2 million total pixels. You can print a 4x5 inch prints taken at this resolution with almost the same quality that you would get from a photo lab. * 2240x1680 - around 4 megapixels. This allows even larger printed photos, with good quality for prints up to 16x20 inches. * 4064x2704 - this resolution is supported by top-of-the-line digital cameras with 11.1 megapixels. At this setting, you can create 13.5x9 inch prints with no loss of picture quality.
High-end consumer cameras can capture up to 12 million pixels. Some professional dSLR cameras support over 16 million pixels, or 20 million pixels for large-format cameras. Hewlett Packard estimates that the quality of the best 35mm film is comparable to a 20 megapixel resolution.
These are the basics of digital imaging. There are many other features found in present-day digital cameras but we will discuss these later on. See you next week.
