Photography is the process of recording pictures by capturing light on a medium, a film or an electronic sensor. Photography has in the last 40 or so years become an very popular hobby but also as a source of income for hundreds of thousands of professional photographers across the globe. The dropping costs of the camera equipment as well as the processing, development and printing materials has enabled the almost epidemic growth in populartity.
The technical process of capturing an image involves light patterns reflected
from objects that expose a sensitive silver 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 advanced photographer can control the camera and lens to expose the light
recording material to the required amount of light to form an image which, after
processing, is converted to a ready to use image. Digital cameras have in recent
years replaced film with an electronic image sensor. This technique is based
on light-sensitive electronics, such as charge-coupled device, or CCD or complementary
metal-oxide-semiconductor. or CMOS technology. The resulting digital image is
stored electronically, but can be easily reproduced on paper or film.
In almost all cameras, the process of obtaining an optimal exposure involves
the useof a few controls to ensure the photograph is clear, sharp and properly
illuminated. Here we cover eleven of the most common controls:
1. Focus: Focus is the adjustment to place the sharpest focus on the subject.
2. Aperture: This is the adjustment of the iris, which controls the amount
of light passing through the lens. Aperture has a clear effect on focus and
depth of field, meaning the range within which objects appear to be sharply
focused.
3. Shutter speed: This is the adjustment of the speed. The speed is expressed
either as fractions of seconds or as an angle with mechanical shutters. Shutter
speed controls the amount of time during which the imaging medium is exposed
to light for each exposure. Shutter speed may be used to control the amount
of light striking the image plane. Fast shutter speeds decrease both the amount
of light and the amount of image blurring from motion of the subject.
4. White balance: This is used on digital cameras as an electronic compensation
for the color temperature associated with a given set of lighting conditions.
White balance ensures that white light is registered as such on the imaging
chip and therefore that the colors in the frame will appear natural. On mechanical,
film-based cameras, this function is served by the film used. In addition to
using white balance to register natural coloration of the image, photographers
may employ white balance in order to obtain a warm color temperature.
5. Metering: This is the measurement of exposure so that highlights and shadows
are exposed optimally. Many modern cameras meter and set exposure automatically.
Before automatic exposure, correct exposure was accomplished with the use of
a separate light metering device or by the photographer's knowledge and experience
of gauging correct settings. To translate the amount of light into a usable
aperture and shutter speed, the meter needs to adjust for the sensitivity of
the film or sensor to light. This is done by setting the "film speed"
or ISO sensitivity into the meter.
6. ISO speed – ISO speeds are used on modern digital cameras as an indication
of the system's gain from light to numerical output and to control the automatic
exposure system. A correct combination of ISO speed, aperture, and shutter speed
leads to an image that has the right illumination.
7. Auto-focus point – on some cameras, the point in the image frame on which the auto-focus system will attempt to focus. Many Single-lens reflex cameras (SLR) has multiple auto-focus points in the viewfinder.
Other elements of the imaging device itself may have an effect on the quality
and/or aesthetic effect of a given photograph; among them are:
8. Focal length as well as type of lens (telephoto or "long" lens,
macro, wide angle, fisheye, or zoom)
9. Any filters that are placed between the subject and the light recording
material, either in front of or behind the lens
10. Sensitivity of the medium to light intensity and color or wavelengths.
11. The nature of the light recording material, for example its resolution
as measured in pixels or grains of silver halide.
The print quality and visual effect can be modified using several techniques:
* Chemicals and process used during film development
* Duration of exposure – equivalent to shutter speed
* Printing aperture – equivalent to aperture, but has no effect on depth
of field
* Contrast
* Dodging – reduces exposure of certain print areas, resulting in lighter
areas
* Burning – increases exposure of certain areas, resulting in darker areas
* Paper texture – glossy, matte, etc
* Paper type – resin-coated (RC) or fiber-based (FB)
* Paper size
* Toners – used to add warm to cool tones to black and white