Film and digital photo part #1
If film cameras were finished and improved more than 160 years digital
technologies of shooting are at infantile age: in laboratory conditions
they are used about 20 years, and in the consumer market digital
cameras have appeared only 7-8 years ago. Certainly, speed of development of
technology for this period simply shakes, but a limit meanwhile is not
achieved, and digital technologies of shooting will develop in
directions of improvement of quality of the image, productivity and convenience
of management. In digital cameras till now there are many sharp
corners, which else it is required to grind. Now the condition of digital
technology of shooting can be compared to other technology of XX century:
automobiles. We have just learned to chromeplate a body, to produce the
engine and to connect headlights. Speaking in other words, digital
technologies have proved the right for a life, bases are already obviously
allocated, and we are expected with rather boring stage of the further
evolution. But, though for us also waits more likely extensive, rather
than intensive, development, this branch nevertheless rivets on itself
steadfast attention. The majority of observers and experts predict,
that the digital photo becomes during very short time the same ordinary
thing as public transport, high-speed highways and other modern miracles.
Till now an overall objective of the digital camera was replacement of
the film camera. But, as films have surpassed theatrical statements, by
opportunities the digital camera now considerably overtakes the film
analogue. Today his(its) prospective use is not reduced any more only to
reception of static images, the camera became a visual communication
facility. For a minute (or even for several seconds) after shooting the
photographer can unpack(print out) the image uses it(him) on
presentation places in the Internet or transfer on the modem (including wireless).
Bases of a film photo
In the usual film camera light is reflected from object or a stage and
passes through transparent glass or plastic lenses which focus it(him)
on a thin flexible slice of plastic (film). The film is covered
photosensitive ������������ with a layer of haloid of silver. Light (photons)
getting on a film leads to to immediate chemical reaction which after
chemical processing helps to show and fix the image on a film. Light
differs on color and intensity that leads to to practically identical
duplication of a stage as a result of chemical reaction. Unique regulators
of light in the usual film camera are ������ (metal either fabric a
curtain or a plate which open quickly and closed for management of time of
an endurance / exposition of a stage on a film) and a diaphragm (the
aperture with the changeable size, allowing to operate quantity(amount)
of light taking place through a lens). Before shooting the photographer
establishes value of endurance(quotation) and the size of a diaphragm.
The diaphragm is usually established manually at rotation ������ on an
objective which in turn mechanically adjusts petals of the aperture
passing light. Certainly, today many cameras (both analog, and digital)
possess some intelligence allowing automatically to choose time of
endurance(quotation) and the size of a diaphragm. But if we will address to
sources the modern film photo in any case is a version of the chemical
and mechanical process invented in 1830 ������ ������� and Fox Talbotom.
Bases of a digital photo
In digital cameras process of reception of the image is much more more
combined. But, as well as in film technology, principles and bases will
be constant the nearest years, irrespective of scale of growth of
technologies.
Film and digital photo part #1
In digital cameras the lens, but instead of focussing the image on a
film also is used, light gets on photosensitive cells of the
semi-conductor chip named a sensor control (image sensor). The sensor control
reacts to received photons that is fixed by the camera. Further the
computing block of the camera analyzes the received information and
defines(determines) necessary values of endurance(quotation) and focus, color
(balance white), necessity of flash, etc. Then a sensor control
Grasps the image and transfers it(him) to chip ATSP (the analog-digital
converter) which analyzes analog electric pulses and will transform
them to a digital kind (a stream of zero and ��������). Using additional
computing capacity (digital cameras can contain some processors and
other chips, including the specialized processors and the main processor),
the data pass the further processing with the help special (dependent
on concrete model / firm) algorithms and will be transformed to a file
of the image which can be seen(overlooked). The file enters the name on
the built - in or external electronic carrier. Further the image can be
transferred on a computer, is deduced(removed) on the printer or the
TV. Equally as it(he) can be seen(overlooked) on the
��-������/view-finder built - in the chamber due to what the user can process the image
with the help of additional algorithms or filters, using the built - in
interface (more often working through the ��-screen) or simply to erase a
unsuccessful picture and to begin all all over again. On all an extent
of this multistage process, "intelligence" of the chamber continuously
interrogates operational system for immediate reaction to actions of
the photographer (which it(he) makes through numerous buttons, levers,
regulators and �� the interface). As you can see, the digital camera is
complex(difficult) system where the set of the data and instructions is
transferred on set of ways. And all this is made in a small easy box
with ����������� which finds room in your palm. The shown process
describes only bases of reception of the digital image. It(him).
Sensor control
Till now almost all chambers in the market were estimated by
quantity(amount) of pixels which the digital camera can remove(take off) (than it
is more than them, the photo will be especially detailed). The
quantity(amount) of pixels depends on the physical size and concentration of
elements on a sensor control. The sensor control is heart of the digital
chamber, and as a sensor control acts ��� or ���� the chip. The sensor
control will consist of set of photosensitive elements (photosites),
containing photo diodes. Elements on the chip are ordered and form a
matrix. Thus, elements of a matrix can be compared to pixels (no less than
to name). Elements react to light and create an electric charge which
size is proportional to quantity(amount) of got light. It is possible to
measure quantity(amount) of pixels of a sensor control on number of
lines and �������� AxB (for example, 640x480), and it is possible - on the
general(common) number of elements (for example, 1000000 pixels). One
million pixels usually name Megapixel (1 MP). In any case the pixel is
the least element of the digital image. Therefore this term is used as
well at the description of monitors and scanners.
Some manufacturers sometimes give in the technical specification two
���������� characteristic ����/��� of a sensor control. First of them
shows the general(common) number of pixels (for example, 3340000 pixels
or 2,11 MP), and the second - number of active pixels which are used for
reception of the image. The difference between these numbers usually
does not exceed 5 %. There are some reasons of such divergence. First, by
manufacture of a sensor control "dark", defective pixels (creation
completely a serviceable sensor control is practically impossible at
existing technologies) are created. Second, some pixels are used for other
purposes, for example, for calibration of signals of a sensor control.
Light does not get on a part of the pixels located on edges(territories).
These pixels help to define(determine) background noise which then will
be subtracted from given other pixels. Also the part of a sensor
control can not be taken into account for creation of the image with a
required format of the staff (the attitude(relation) of quantity(amount) of
points across to quantity(amount) of points on a vertical). By the way,
dependence of the size of a photo on number of pixels not linear, but
logarithmic. Transition from 3 MP to 4 MP to a sensor control increases
the size of the image not by 25 %, and on smaller value. For this
reason even in the newest digital cameras with the increased concentration
of pixels on a sensor control the size of the image insignificantly
differs from the previous models, that hardly so it is important for the
majority of users.
Now all digital chambers of an amateur level use one ���� or ��� a
sensor control. The some people high-end professional devices (no less than
many portable videocameras) use some sensor controls. In them entering
light is divided(shared) by a prism on a number(line) of
bunches(beams), each of which gets on the sensor control. Such technology allows to
prevent imposing of colors (when borders of red, dark blue and green
color are shifted on the image). However similar chambers demand accurater
process of manufacturing, and owing to presence of a prism they more
�������� and are less hardy. Also in them the improved optics so the
total price of such chamber is essentially higher should be used. That is
interesting, use of several sensor controls does not lead to to linear
growth of quantity(amount) of pixels. In the majority of cameras (no
less than in multitouch videocameras) it is used three separate ����/��� a
sensor control for red, green and dark blue color. Each of them
receives 1/3 color information. Thus, at use of three 3 MP sensor controls
they will work as one 3 MP a sensor control. However frequently in digital
cameras the mechanism of use of the information received from sensor
controls, differs. Actually it(he) depends on model and from the
manufacturer. In some three-touch cameras each sensor control grasps 1/3 from
the sanction of the full image, and then there is an interpolation.
Other chambers use any combination of the main colors on
Each sensor control also will involve complex(difficult) algorithms
for reception of the image. For example, already not issued(not were
issued) Minolta RD-175 it has been equipped with three ��� the sensor
controls, two of which were green, and the third was red - dark blue. (Such
doubling of a green sensor control reminds technology Bayer Pattern
about which it will be told below). Each of sensor controls RD-175
contained less than 1 MP, but due to the further mathematical transformation
the received image has consisted of 1,7 Megapixels. In many digital
chambers only the part of pixel reacts to light, therefore it is important
to direct as much as possible light on the necessary area of pixel
(this phenomenon refers to as factor of filling, fill factor). For this
purpose on sensor controls of the majority of cameras of an amateur level
the microlenses settling down directly above each pixel and directing
photons directly on photosensitive area (well) are used. Photons will be
transformed in ��������� with the help of the silicon photo diode which
is settling down in the top part of photosensitive area, and the area
works as the condenser as possesses an opportunity of preservation of an
electric charge. As sensor controls inherently are the black-and-white
devices which are not distinguishing color, in digital cameras the file
of color optical filters (color filter array, CFA), settling down
between a microlens and photosensitive area of pixel more often is used.
With the help of an optical filter to each pixel the color is
appropriated(given). Manufacturers of digital chambers use various architecture of
optical filters, as a rule, ������������� a combination of primary
colours (red, green and dark blue) or complementary colors (blue, purple
and yellow). But in any case the principle of work of the filter consists
in the miss(passing) only the necessary color (with the certain length
of a wave). Thus it is required to reduce displays of color artefacts
and to avoid mutual influence of the next pixels, at the same time,
keeping correct �������������.
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