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Introduction
to Photography
in
English.
Part I
In
This section of
Ferreira
Photo.Com
you
will find a short
induduction
to Photography
in
English.
Photography
Photography is the process of recording pictures by
means of capturing light on a light-sensitive medium, such as a film
or electronic sensor (in Digital Photography). Light patterns
reflected or emitted from objects expose a sensitive silver halide
based chemical or electronic medium during a timed exposure, usually
through a photographic lens in a device known as a camera that also
stores the resulting information chemically or electronically. The
camera or camera obscura is the image-forming device, and
photographic film or a silicon electronic image sensor is the sensing
medium. The respective recording medium can be the film itself, or a
digital electronic or magnetic memory. Photographers control the
camera and lens to "expose" the light recording material
(such as film) to the required amount of light to form a "latent
image" (on film) or "raw file" (in digital cameras)
which, after appropriate processing, is converted to a usable image.
Modern digital cameras replace film with an electronic image sensor
based on light-sensitive electronics such as charge-coupled device
(CCD) or complementary metal-oxide-semiconductor (CMOS) technology.
The resulting digital image is stored electronically, but can be
reproduced on paper or film.
Camera:
A camera is a device used to capture images, either as
still photographs or as sequences of moving images (movies or
videos). The term comes from the Latin camera obscura for "dark
chamber" for an early mechanism of projecting images where an
entire room functioned as a real-time imaging system; the modern
camera evolved from the camera obscura.
Aperture:
In optics, an aperture is a hole or an opening through
which light is admitted. More specifically, the aperture of an
optical system is the opening that determines the cone angle of a
bundle of rays that come to a focus in the image plane. The aperture
determines how collimated the admitted rays are, which is of great
importance for the appearance at the image plane. If the admitted
rays also pass through a lens, highly collimated rays (narrow
aperture) will result in sharpness at the image plane, while
uncollimated rays (wide aperture) will result in sharpness for rays
with the right focal length only.
Exposure:
Exposure is the total amount of light allowed to fall
on the photographic medium (photographic film or image sensor) during
the process of taking a photograph. Exposure is measured in lux
seconds, and can be computed from exposure value (EV) and scene luminance.
Depth of Field:
In optics, particularly as relates to film and
photography, the depth of field (DOF) is the distance in front of and
beyond the subject that appears to be in focus. Although a lens can
precisely focus at only one distance, the decrease in sharpness is
gradual on either side of the focused distance, so that within the
DOF, the unsharpness is imperceptible under normal viewing conditions.
For some images, such as landscapes, a large DOF may
be appropriate, while for others, such as portraits, a small DOF may
be more effective.
Lens:
A photographic lens (also known as objective lens or
photographic objective) is an optical lens or assembly of lenses used
in conjunction with a camera body and mechanism to make images of
objects either on photographic film or on other media capable of
storing an image chemically or electronically.
Zoom
lens:
Zoom lenses, have a focal length that varies as
internal elements are moved, typically by rotating the barrel or
pressing a button which activates an electric motor. Commonly, the
lens may zoom from moderate wide-angle, through normal, to moderate
telephoto; or from normal to extreme telephoto. The focal length of a
zoom lens is not fixed; instead it can be varied between a specified
minimum and maximum value. Modern lens technology is such that the
loss of image quality in zoom lenses (relative to non-zoom lenses) is
minimal, and zoom lenses have become the standard lenses for SLRs and
DSLRs. This is different from only 20 years ago when, due to image
quality concerns, most professional photographers still relied
primarily on standard non-zoom lenses.Zoom lenses are often described
by the ratio of their longest to shortest focal lengths. For example,
a zoom lens with focal lengths ranging from 100 mm to 400 mm may be
described as a 4:1 or "4×" zoom. Typical zoom lenses
cover a 3.5× range, for example from 24 - 90 mm (standard zoom)
or 60 - 200 mm (telephoto zoom). "Super-zoom" lenses with a
range of 10× or even 14× are becoming more common, although
the image quality does typically suffer a bit compared with the more
traditional zooms. The maximum aperture for a zoom lens may be same
for all focal lengths, but it is more common that the maximum
aperture is greater at the wide-angle end than at the telephoto end
of the zoom range. For example, a 100 mm to 400 mm lens may have a
maximum aperture of 4.0 at the 100 mm end but only 5.6 at the 400 mm
end of the zoom range.
Wide
Angle:
A wide-angle lens is a lens whose focal length is
substantially shorter than the focal length of a normal lens for the
image size produced by the camera, whether this is dictated by the
dimensions of the image frame at the film plane for film cameras
(film format)[1] or dimensions of the photosensor for digital cameras.
Teleconberters:
A teleconverter is a secondary lens which is mounted
between the camera and a photographic lens. Its job is to enlarge the
central part of an image obtained by the objective lens. For example
a 2× teleconverter enlarges the central 12×18 mm part of an
image to the size of 24×36 mm. Teleconverters are typically made
in 1.4×, 2× and 3× models. The use of a 2×
teleconverter (or doubler) gives the effect of using lens with twice
the focal length. It also decreases the intensity of the light
reaching the film by the factor of 4 (an equivalent of doubling the
focal ratio) as well as the resolution (by the factor of 2).
Prime
lens:
Standard non-zoom lenses are called prime lenses or
simply "primes". Their advantage, in addition to typically
giving a slightly better image quality, is that they are smaller,
lighter and cheaper than a zoom lens of the same quality. A prime
lens may also be "faster" and have a larger maximum
aperture (smaller f-number), so it can be used with less light (with
the same shutter speed), and can provide less depth of field in
situations where this is desirable.
Macro:
Macro lenses are designed for extreme closeup work.
Such lenses are popular for nature shooting such as small flowers, as
well as for many technical applications. Occasionally, macro lenses
are used for close portraits.
Fisheye:
In photography, a fisheye lens is a wide-angle lens
that takes in an extremely wide, hemispherical image. Originally
developed for use in meteorology and astronomy and called
"whole-sky lenses", fisheye lenses quickly became popular
in general photography for their unique, distorted appearance. They
are often used by photographers shooting broad landscapes to suggest
the curve of the Earth. Hemispherical photography is used for various
scientific purposes to study plant canopy geometry and to calculate
near-ground solar radiation. The focal lengths of fisheye lenses
depend on the film format. For the popular 35 mm film format, typical
focal lengths of fisheye lenses are between 8 mm and 10 mm for
circular lenses, and 15-16 mm for full-frame lenses. All the
ultra-wide angle lenses suffer from some amount of barrel distortion.
While this can easily be corrected for moderately wide angles of
view, rectilinear ultra-wide angle lenses with angles of view greater
than 90 degrees are difficult to design.
Photographic
Filter:
In photography, a filter is a camera accessory
consisting of an optical filter that can be inserted in the optical
path. The filter can be a square or rectangle shape mounted in a
holder accessory, or, more commonly, a glass or plastic disk with a
metal or plastic ring frame, which can be screwed in front of the lens.
Filters allow added control for the photographer of
the images being produced. Sometimes they are used to make only
subtle changes to images; other times the image would simply not be
possible without them.
Most use Filters:
Polarizer
A polarizing filter, used both in color and black and
white photography, can be used to darken overly light skies. Because
the clouds are relatively unchanged, the contrast between the clouds
and the sky is increased. Atmospheric haze and reflected sunlight are
also reduced, and in color photographs overall color saturation is
increased. Polarizers are often used to deal with situations
involving reflections, such as those involving water or glass,
including pictures taken through glass windows.
Neutral
Density:
A Neutral Density (ND) filter creates a reduction in
light that is neutral and equal for the film or sensor area. This
filter is often used to allow for longer exposure times whenever a
longer exposure would normally create over exposure in the camera.
A Graduated Neutral Density (GND) filter is a neutral
density filter that varies the effect with a gradient so it can be
used to compress dynamic range across the entire scene. This can be
beneficial when the difference between highlights and shadows of a
scene are too great to allow for proper exposure for both.
Clear:
Clear filters, also known as window glass filters or
optical flats, are completely transparent, and (ideally) perform no
filtering of incoming light at all. The only use of a clear filter is
to protect the front of a lens.
Ultraviolet
filter:
UV filters are used to reduce haziness created by
ultraviolet light. A UV filter is mostly transparent to visible
light, and can be left on the lens for nearly all shots. UV filters
are often used for lens protection, much like clear filters.
Infrared
(IR) Filter:
In infrared photography, the film or image sensor used
is sensitive to infrared light. The part of the spectrum used is
referred to as near-infrared to distinguish it from far-infrared,
which is the domain of thermal imaging. When these filters are used
very interesting effects can be obtained.
RAW Format
RAW file format is the uncompressed, unprocessed data
file captured by the camera's image sensor. The camera will
ignore your white balance, sharpening, contrast and saturation
settings. Instead of applying them to the RAW data, it will save
those settings in a separate header associated with the RAW data. In
addition to raw files from cameras, raw data from film scanners can
also be referred to as digital negatives. Likewise, the process of
converting a raw image file into a viewable format is sometimes
called developing a raw image, by analogy with the film development.
The fascination with RAW is that it seems to magically
give you the ability to "correct your mistakes. Remember that
when you save an image in RAW, your image settings are ignored as far
as applying them to the image, and are instead saved in a header.
When you open the RAW data in your image editing
software (with the appropriate RAW plug-in installed, since every
manufacturer encodes RAW a little differently), that header is read
and used to display an image of the RAW data.
You may now manually adjust the settings and see the
effect on the RAW data -- giving the effect of being able to
magically "correct your mistakes." When you are happy with
the adjustments, you would then typically save a copy as JPEG.
RAW is therefore a powerful option that most advanced
digital cameras make available to photographers who do not want the
camera to apply any in-camera processing to the captured RAW data,
preferring to do that themselves in post-processing.
Rule of thirds:
The rule of thirds is a compositional rule of thumb in
photography and other visual arts such as painting and design. The
rule states that an image can be divided into nine equal parts by two
equally-spaced horizontal lines and two equally-spaced vertical
lines. The four points formed by the intersections of these lines can
be used to align features in the photograph. Proponents of this
technique claim that aligning a photograph with these points creates
more tension, energy and interest in the photo than simply centering
the feature would.
Click
here to continue the Part II of
About
Photography,
in
English version.
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