Digital technology is developing at breakneck speed.
I think we have just got used to ignore it.
Someone said that if cars evolved at the same rate as computers, a Rolls-Royce today would cost ten dollars, had a motor the size of a matchbox and can travel a thousand kilometers to one liter of gasoline.
To paraphrase, we can say that if film photography developed at the same rate as the digital, the average film would have been wide, with a silk thread, and would be housed with thousands of cadres.
It is impossible to overestimate the contribution that the “figure” has in everyday life: it is enough to recall that many of today’s mobile phone has a camera which allows to get quite tolerant of quality card format of 9 × 12.
Some history
Digital cameras are born from the same source as the television.
Until now, the vast majority of digital cameras use a sensor based on CCD (Charged Coupled Device), it is a CCD (charge-coupled device) – the same technology as that used in the very first black and white television cameras.
Actually, the first domestic digital cameras were only a design for a video camera, an image which was put “on pause”, digitized and recorded on a floppy disk or mini-disk, and then play on your TV screen.
The first such device manufactured by Sony appeared in 1981 and called Sony Mavica (Magnetic Video Camera, video camera with a magnetic recording).
Mavica was a full-fledged SLR with interchangeable lenses and had a resolution of 570 × 490 pixels (0.28 megapixel), the recording was done on a special 2-inch floppy disk (the usual for us, albeit slowly receding in the history of the 3.5-inch floppy disks were put on the market all the same Sony later).
Special distribution Mavica not received until 1986, when similar products were issued by Canon and Nikon.
However, digital images as a class appeared much earlier: the first purely digital images were obtained with the mapping of the lunar surface by U.S. astronauts and transmitted to Earth in the mid 60’s.
Also, digital images were transmitted from American spy satellites in the 70 years of the last century.
First video camera Sony Mavica
Then, in the 70’s, extensive development in the field of digital photography led the company Kodak, which received as a result of a series of products for digital imaging.
Development of a standard Kodak Photo CD in 1990 and launched into production in 1991, together with professional Nikon SLRs Nikon F3, fitted instead of the mechanism of the film broaches digital sensors, has completed the first stage of the development of digital photography.
Nor can not see what Kodak has introduced in 1986 in the use of the term “megapixels”, creating an industrial design CCD-sensor with a resolution of 1.4 megapixel.
There is, incidentally, a certain grim humor in the fact that these technologies are now contributing to the reduction by Kodak jobs and the loss of her significant segment of home photos.
Really championship in the production of high-grade digital video camera owned by Fuji, which released in 1988, with Toshiba camera DS-1P, based on CCD-sensor with a resolution of 0.4 megapixel.
DS-1P was also the first camera, registering the image is not on a magnetic disk, and removable memory card, SRAM (Static RAM) with built-in order to maintain the integrity of the data pack.
In the same year, Apple with Kodak produces the first program for image processing on the computer – PhotoMac.
Just a year later the company Letraset produces a much more advanced program Color Studio 1.
In the early 90’s digital photography has developed in the professional sphere, and the price of solutions ranged from five to fifteen thousand dollars.
There were also the first digital backdrops for medium format cameras.
Mid-90’s exit was marked at once the whole series of digital cameras, consumer level.
The first domestic digital cameras cheaper thousands of dollars came in 1993, but the real marketing breakthrough made in February 1994, already holding the nose strictly to the wind, Apple has a product Apple QuickTake 100.
The camera was released in the body, reminiscent of binoculars (popular in those years form for the video camera) and allows you to store the internal Flash-memory-eight images size is 640 × 480 (0.3 MP), or 32 shots with half the resolution of 320 × 200.
Connect the camera to a computer via serial port, fed by three AA batteries, size and cost less than eight hundred dollars.
The product is based on the large number of patents Kodak.
Following Apple hauled closest competitors: own elaboration Kodak DC 40 (March 1995), Casio QV-11 (end of 1995, the first a digital camera with LCD-display and the very first – from turning the lens), and finally, the development of Sony – the first in the line camera, called simply Cyber-Shot, no letters and indices (1996).
Also in 1994 appeared the first memory card format Compact Flash and SmartMedia, the volume from 2 to 24 MB.
The first mass digital camera Apple QuickTake 100
All the 90-ies Kodak continues to work marketing engine, giving birth to life all the new products, including joint – digital kiosks, recording images on Photo CD with Kinko, and Microsoft, a system for sharing digital photos on the Internet in conjunction with IBM, the first color photo printer conjunction with Hewlett-Packard.
That’s the end of XX century was the stage of explosive development of digital photography, when for some 10 years of digital camera has evolved from an expensive professional devices in consumer toy, available to everyone.
It happened due to the development and output of industrial volumes of digital fabrication technologies photosensors.
Sensors, their sizes and types
Imagine a large gym with an old and leaky roof.
To find out which parts of the roof are in the emergency state, and which until the repair can wait, we have placed throughout the hall empty buckets, aligned on a square grid, and wait for rain.
After the rain we measure how much water had accumulated in each bucket, and on this basis make conclusions about the state of the roof as a whole.
Some work this way all digital photoelectric sensors: after opening the gate sensing elements, which focuses the image, store a charge proportional to the level of light.
After closing the shutter auxiliary circuit reads the signal from each element, amplifies and converts it into digital form.
Small nestykovochka: since each photosensitive element measures only the level of illumination, described the scheme has only black and white vision.
Previously, expensive cameras (and still in high-quality video cameras) had three sensors, one for each of the primary colors.
From a certain point, when the cost of the final product was the critical parameter, the scheme was replaced a so-called color Bayer array.
In this half of the array of pixels arranged in a checkerboard pattern, is responsible for the green color, to which the human eye is most sensitive, and another 25% of pixels read, respectively, red and blue.
The values of the other two colors in each pixel are interpolated.
It is important to understand: every second pixel in the resulting in the highest resolution sensor images is set to red and blue channels, calculated by bicubic interpolation method, and the picture there is no point, for which the measured value of at least two of the three channels.
Add to this the inevitable errors of digitization – and the result at the final image may appear different artifacts, which will be much discussed below.
However, mathematics does not stand still, and have recently begun to apply more complex interpolation algorithms.
Also recently the firm Sony has introduced a new color scheme RGBE, where E means «emerald», that is emerald.
In this scheme, two “green” pixel is slightly different from each other by color, allowing, thus, increase the color gamut of the sensor (but not correcting the situation with the artifacts of interpolation).
Also we should mention here the innovative technology of SuperCCD Fuji, which octagonal pixels arranged in a checkerboard pattern, even though it’s complicated interpolation, but allows you to effectively get rid of the artifacts.
Fuji SuperCCD
Another important feature still remaining scourge of all digital cameras – a digital noise – namely, dot interference is especially noticeable in low light conditions.
They have the same nature as the noise on the film: when the light receiver gets enough light, the ratio of the random scatter of the levels of individual pixels in the sensor (or individual crystals of silver in the film) to the useful signal becomes higher.
It is convenient again to imagine the long rows of buckets: when the rain is small – difficult to say which of the two neighboring bucket filled with more than after a heavy downpour, where the difference is visible immediately.
Digital noise – an integral part of digital photography, and the fight with him – one of the main objectives of producers of sensors and software for the cameras.
By the way, buying a first digicam people often ask: why in the characteristics of cells often show two digits of the sensor permits: general and effective?
My answer is: it is done just to combat noise.
Several (6 to 12) extreme series of pixels on the sensor closed impermeable filter, and use them to score is the average noise level, which is then subtracted from the final image.
This is especially effective for combating the “dark currents” – noises caused by random thermal motion of the electron sensor in the absence of illumination (with a closed gate).
Another obvious way to deal with the noise – it increases the area of the sensor.
Indeed, the more it is, the greater the area of each photosensitive element, he, in turn, registers more light, and the measurement error becomes smaller.
However, it is not so simple: the price sensors, especially built on the technology of CCD, is growing disproportionately to the growth of their area.
In addition, the smaller the sensor, the smaller the mandatory requirements to the geometry of optics, the cheaper the lens and the more he may be a range of focal lengths (or, more simply, zoom).
You’ve probably already met several times the size designation of sensors of 1 / 1.
8 “, 1 / 2.
7, 2 / 3 “and so
And would like to know what they mean in reality.
Cause you pain: these figures have little relevance to the real size sensors and not represent the real, and so-called “intensified vidicon” inches.
The manner denoted as the size went from the time of inception TV when the receiver element in the camera is an electronic tube (vidicon), and the size meant its diameter (which was supposed to fit with a stock photo being taken).
For coarse prikidok can assume that “intensified vidicon” and real inches belong as 3 to 2.