Digital Cameras 2U

Digital camera Connectivity

Many digital cameras can connect directly to a computer to transfer data:

Early cameras used the PC serial port. USB is now the most widely used method ( Most cameras are viewable as USB Mass Storage), though some have a FireWire port.
Other cameras use wireless connections, via Bluetooth or IEEE 802.11 Wi-Fi, such as the Kodak EasyShare One.
Increasingly popular is the use of a card reader which may be capable of reading several types of storage media, and transferring at high speed to the computer. This also avoids draining the camera battery during the download process as the device takes power from the USB port.

Most modern cameras use the PictBridge standard to send data directly to printers without the need of a computer.

Digital camera Interpolation

Image color or resolution interpolation is used unless the camera uses a beam splitter single-shot approach, three-filter multi-shot approach, or Foveon X3 sensor currently used in Sigma SD10 DSLR and Polaroid x530 point and shoot. The software specific to the camera interprets the information from the sensor to obtain a full color image. This is because in digital images, each pixel must have three values for luminous intensity, one each for the red, green, and blue channels. A normal sensor element cannot simultaneously record these three values.

The Bayer filter pattern is typically used. A Bayer filter pattern is a 2×2 pattern of light filters, with green ones at opposite corners and red and blue elsewhere. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving 2 different hues of green. This provides a wider color gamut, but requires a slightly more complicated interpolation process.

The luminous intensity color values not captured for each pixel can be interpolated (or guessed at) from the values of adjacent pixels which represent the color being calculated. In some cases, extra resolution is interpolated into the image by shifting photosites off of a standard grid pattern so that photosites are adjacent to each other at 45 degree angles, and all three values are interpolated for “virtual” photosites which fall into the spaces at 90 degree angles from the actual photosites.

Digital camera Pixels

The resolution of a digital camera is determined by the camera sensor (usually a Charged Coupled Device or CCD chip) that turns light into digital information, replacing the job of film in traditional photography. It represents this light value in pixels, which are little squares (on a CCD) that make up the image. Each pixel can store one digital value, which can then be recalled and put with other pixel values to generate a digital photograph.

The more pixels the camera can recall, the better the resolution it can offer. Cameras are usually characterised by the number of megapixels they offer, when a million pixels is equal to a megapixel.

The arrival of true digital cameras

The first true digital camera that recorded images as a computerized file was likely the Fuji DS-1P of 1988, which recorded to a 16 MB internal memory card that used a battery to keep the data in memory. This camera was never marketed in the United States. The first commercially 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, often Nikons. It used a 1.3 megapixel sensor and was priced at $13,000.

The move to digital formats was helped by the formation of the first JPEG and MPEG standards in 1988, which allowed image and video files to be compressed for storage. The first consumer camera with an LCD 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 marketplace for consumer digital cameras was originally low resolution (either analog or digital) cameras built for utility. In 1997 the first megapixel cameras for consumers were marketed. The first camera that offered the ability to record video clips may have been the Ricoh RDC-1 in 1995.

1999 saw the introduction of the Nikon D1, a 2.74 megapixel camera that was the first digital SLR developed entirely by a major manufacturer, and at a cost of under $6,000 at introduction was affordable by professional photographers and high end consumers. This camera also used Nikon F-mount lenses, which meant film photographers could use many of the same lenses they already owned.

2003 saw the introduction of the Canon Digital Rebel, also known as the 300D, a 6 megapixel camera and the first DSLR priced under $1,000, and marketed to consumers.

Early development of the digital camera

Texas Instruments designed a filmless analog camera in 1972, but it is not known if it was ever built. The first recorded attempt at building a digital camera was by Steve Sasson, an engineer at Eastman Kodak. It used the then-new solid state CCD chips developed by Fairchild Semiconductor in 1973. The camera weighed 8 pounds (3.6 kg), recorded black and white images to a cassette tape, had a resolution of 0.01 megapixel (10,000 pixels), and took 23 seconds to capture its first image in December of 1975. The prototype camera was a technical exercise, not intended for production, and it still existed as of 2005.

Digital cameras, in the sense of a device meant to be carried and used like a handheld film camera, appeared in 1981 with the demonstration of the Sony Mavica (Magnetic Video Camera). This is not to be confused with the later cameras by Sony that also bore the Mavica name. This was an analog camera based on television technology that recorded to a 2 × 2 inch “video floppy”. In essence it was a video movie camera that recorded single frames, 50 per disk in field mode and 25 per disk in frame mode. The image quality was considered equal to that of then-current televisions.

Analog cameras do not appear to have reached the market until 1986 with the Canon RC-701. Canon demonstrated this model at the 1984 Olympics, printing the images in newspapers. Several factors held back the widespread adoption of analog cameras; the cost (upwards of $20,000), poor image quality compared to film, and the lack of quality affordable printers. Capturing and printing an image originally required access to equipment such as a frame grabber, which was beyond the reach of the average consumer. The “video floppy” disks later had several reader devices available for viewing on a screen, but were never standardized as a computer drive.

The early adopters tended to be in the news media, where the cost was negated by the utility and the ability to transmit images by telephone lines. The poor image quality was offset by the low resolution of newspaper graphics. This capability to transmit images without a satellite link was useful during the Tiananmen Square protests of 1989 and the first Gulf War in 1991.

The first analog camera marketed to consumers may have been the Canon RC-250 Xapshot in 1988. A notable analog camera produced the same year was the Nikon QV-1000C, which sold approximately 100 units.[citation needed] It recorded images in greyscale, and the quality in newspaper print was equal to film cameras. In appearance it closely resembled a modern digital single-lens reflex camera.

Professional modular digital camera systems

When digital cameras became common, a question many photographers asked was if their film cameras could be converted to digital. The answer was yes and no. For the majority of 35 mm film cameras the answer is no, the reworking and cost would be too great, especially as lenses have been evolving as well as cameras. For the most part a conversion to digital, to give enough space for the electronics and allow an LCD screen to preview, would require removing the back of the camera and replacing it with a custom built digital unit.

Many early professional SLR cameras, such as the NC2000 and the Kodak DCS series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being a digital “back” the body was mounted on a large and blocky digital unit, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.

A notable exception was a device called the EFS-1, which was developed by Silicon Film from ca. 1998–2001. It was intended to insert into a film camera in the place of film, giving the camera a 1.3 MP resolution and a capacity of 24 shots. Units were demonstrated, and in 2002 the company was developing the EFS-10, a 10 MP device that was more a true digital back.

A few 35 mm cameras have had digital backs made by their manufacturer, Leica being a notable example. Medium format and large format cameras (those using film stock greater than 35 mm), have users who are capable of and willing to pay the price a low unit production digital back requires, typically over $10,000. These cameras also tend to be highly modular, with handgrips, film backs, winders, and lenses available separately to fit various needs.

The very large sensor these backs use lead to enormous image sizes. The largest in early 2006 is the Hasselblad H2D, which makes images 39 MP in size from a 36.7 mm × 49 mm sensor. Medium format digitals are geared more towards studio and portrait photography than their smaller DSLR counterparts, the ISO sensivity in particular tends to have a maximum of 400, versus 3200 for some DSLR cameras.

Since the first backs were introduced there have been three main methods of “capturing” the image, each based on the hardware configuration of the particular back.

The first method is often called “Single Shot,” in reference to the number of times the camera’s sensor is exposed to the light passing through the camera lens. Single Shot capture systems use either one CCD with a Bayer filter stamped onto it or three separate CCDs (one each for the primary additive colors red, green and blue) which are exposed to the same image via a beam splitter.

The second method is referred to as “Multi-Shot” because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single CCD with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method utilized a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to “stitch” together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without stamping a Bayer filter onto the chip.

The third method is called “scan” because the sensor moves across the focus plane much like the sensor of a desktop scanner. These CCDs are usually referred to as “sticks” rather than “chips” because they utilize only a single row of pixels (more properly “photosites”) which are again “stamped” with the Bayer filter.

The fourth method is a rotational scan of a linear sensor. A digital rotating line camera offers images of very high resolution.

The choice of method for a given capture is of course determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject which moves (like people or objects in motion) with anything but a single shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scan-backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.

Digital single-lens reflex camera

DSLRs are conceived for professional photographers and are well adapted for action photography or specialized uses. They are based on film single-lens reflex cameras and retain their main features : image composing done through the optical viewfinder using a mirror reflected image and exchangeable lenses, albeit a few early SLR digital cameras like the Olympus E-10 have a fixed lens.

The ability to change lenses gives the same benefits as in film cameras, allowing tailoring a lens to an intended use instead of a compromise. They can use the same lenses as their film counterparts, but the sensor is usually smaller than that of 35 mm film. A common term is “APS class,” being the same general size as APS film. Focusing on the smaller area results in digital cameras having a zoom of 1.5 to 2.0 times over the same lens on a 35 mm film camera. Thus a 50 mm lens on a DLSR with a 1.5 crop ratio would show the same angle of view as a 75 mm lens on a 35 mm camera.

DSLR cameras have larger image sensors than compacts or prosumers, and thus higher sensitivity in dim lighting and less noise overall in the pictures they take. They usually are instantly on and the autofocus and operation is faster. Most of them can save in JPEG and raw formats even simultaneously.

They are bulkier, heavier and frequently much more expensive. Two characteristics many consumers are surprised to find due to the reflex viewfinder is they cannot record movies and the screen is only for reviewing pictures. All composing is done through the optical viewfinder which has more resolution than an electronic viewfinder and does not produce any delay. In 2006 the Olympus E-330 is the only DSLR that can use the LCD for a live preview, and will be joined by the Panasonic Lumix DMC-L1.

Prosumer cameras

Prosumer cameras or extended zoom cameras form a general group of higher end cameras that physically resemble SLR “professional” cameras and share some features, but are still geared towards consumers. Thus, the name prosumer from professional and consumer. These cameras tend to have a large optical zoom lens, which compromises a “do it all” ability with barrel distortion and pincushioning. Prosumer cameras are sometimes marketed as and confused with digital SLR cameras since the bodies resemble each other. The distinguishing characteristics are that prosumer cameras do not have a removable lens (although accessory wide angle or telephoto lenses can be attached to the front of the main lens), can usually take movies, record audio and the scene composition is done with either the LCD display or the electronic viewfinder (EVF). The overall performance tends to be slower than a true digital SLR, but they are capable of very good image quality while being more compact and lighter than DSLRs. The high-end models of this type have comparable resolutions to low and mid-range DSLRs Many of the these cameras can save in JPEG or .RAW format.

Compact digital cameras

Also called digicams, this encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They tend to have significantly smaller zooms than prosumer and DSLR cameras. They have an extended depth of field. This allows objects at a larger range of depths to be in focus, which accounts for much of their ease of use. It is also part of the reason professional photographers find their images flat or artificial-looking. They excel in landscape photography and casual use. They typically save pictures in only the JPEG file format.

Digital Still Cameras

Digital still cameras are cameras whose primary purpose is to capture photography in a digital format. Initially, a digital camera was characterized by the use of flash memory and USB or FireWire for storage and transfer of still photographs (though some early cameras used a serial port connection), and this is still the common meaning of the unadorned term. Many modern digital photography cameras have a video function, and a growing number of camcorders have a still photography function. However, even a low-end still camera can take far better still pictures than a mid-range video camera, and mid-range still cameras have much lower video quality than low-end video cameras. In addition, some newer camcorders record video directly to flash memory and transfer over USB and FireWire. Among digital still cameras, most have a rear LCD for reviewing photographs. They are rated in megapixels; that is, the product of their maximum resolution dimensions in millions. The actual transfers to a host computer are commonly carried out using the USB mass storage device class (so that the camera appears as a drive) or using the Picture Transfer Protocol and its derivatives, in addition firewire is becoming more popular and supported among more digital cameras. All use either a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor or novel sensors based upon either of those two principles, i.e. chips comprised of a grid of phototransistors to sense the light intensities across the plane of focus of the camera lens. CMOS sensors are differentiated from CCDs proper in that it uses less power and a different kind of light sensing material, however the differences are highly technical and many manufacturers still consider the CMOS chip a charged coupled device. For our purposes, a chip sensor is a CCD.