The ABC of Photography
A
Aberration
An optical fault in a lens that creates a less-than-perfect image.
In optics, the aberration is a property of optical systems, such as lenses that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration.
There are six types of optical aberration:
- Astigmatism
- Chromatic Aberration
- Coma
- Distortion
- Field Curvature
- Spherical Aberration
Examples:
There is so much more to be researched on this specific topic!
Abstract
In photography, this term refers to images that concentrate on aspects of a subject such as shape, form, colour, and texture. Instead of a straightforward representation of a subject.
Definition of Abstract Photography.
Abstract images are conceived or imagined outside of ‘reality’. They can encompass a huge variety of subject matter, take us out of our comfort zone, make us question what we see, or invite us to enter another realm. Sometimes called non-objective, experimental, conceptual or concrete photography, is a means of depicting a visual image that does not have an immediate association with the object world and that has been created through the use of photographic equipment, processes or materials.
An abstract photograph may isolate a fragment of a natural scene in order to remove its inherent context from the viewer, it may be purposely staged to create a seemingly unreal appearance from real objects, or it may involve the use of color, light, shadow, texture, shape and/or form to convey a feeling, sensation or impression. The image may be produced using traditional photographic equipment like a camera, darkroom or computer, or it may be created without using a camera by directly manipulating film, paper or other photographic media, including digital presentations.
Adjustment layer
This is a layer containing an image adjustment or effect instead of image content. Like a red Cellophane overlay on a print, an adjustment layer will alter the appearance of layers below it, but not actually alter their content, making adjustment layers a cornerstone of reversible, ‘non-destructive’ editing. The adjustment can be altered, hidden or removed at any point. When you add an adjustment layer, a mask is also automatically created, so that the effect can be applied to a lesser extent (or not at all) in particular areas of the image. The Adjustment Layers in Photoshop are a group of super useful, non-destructive image editing tools that add color and tonal adjustments to your image without permanently changing its pixels. With the adjustment layers, you can edit and discard your adjustments or restore your original image at any time.
Adobe Camera Raw
A free plugin used by Photoshop and Elements to process and edit raw files. Adobe Camera Raw is frequently updated to support the newest camera models. Adobe Camera Raw, which lets you import and enhance raw images, has been a must-have tool for professional photographers right since it was first released in 2003. Applications that support Adobe Camera Raw include Photoshop, Photoshop Elements, After Effects, and Bridge. Additionally, Adobe Lightroom is built upon the same powerful raw image processing technology that powers Adobe Camera Raw.
AE
An abbreviation for automatic exposure. This camera feature enables the user to determine the shutter speed and aperture for an image, usually via a TTL (through-the-lens) exposure meter. Automatic exposure mode (also called automatic exposure and abbreviated as AE) is a standard feature on digital cameras that will automatically determine the correct exposure for pictures without any user input other than to select the AE option before taking a picture.
AEL
Automatic exposure lock. This is a push-button control that enables you to select the part of the scene from which the camera takes its meter reading, and then lock this setting while the image is re-framed for better composition. The auto-exposure lock (AE-L) function on a DSLR camera lets you physically lock the exposure reading from anywhere in the scene. You can use it on its own or at the point where you focus the image. Just about all DSLR cameras have an auto exposure lock button.
AF
Stands for autofocus, a function first introduced on cameras in the late 1970s, in which the lens is adjusted automatically to bring the designated part of the image into sharp focus. Almost all modern lenses for digital SLRs have AF, which is achieved via one or more sensors and a motor either integrated into the lens itself or the camera body.
An autofocus (or AF) optical system uses a sensor, a control system, and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication. Autofocus methods are distinguished by their type as being either active, passive or hybrid variants.
Autofocus systems rely on one or more sensors to determine the correct focus. Some AF systems rely on a single sensor, while others use an array of sensors. Most modern SLR cameras use through the lens optical sensors, with a separate sensor array providing light metering, although the latter can be programmed to prioritize its metering to the same area as one or more of the AF sensors.
Through-the-lens optical autofocusing is now often speedier and more precise than can be achieved manually with an ordinary viewfinder, although more precise manual focus can be achieved with special accessories such as focusing magnifiers. Autofocus accuracy within 1/3 of the depth of field (DOF) at the widest aperture of the lens is common in professional AF SLR cameras.
AF illuminator
This is a system used by some cameras and flashguns to assist autofocus in low light. A pattern of red light is projected on to the subject, which aids the contrast-detection autofocus to adjust the lens correctly.
AF-S
This stands for ‘autofocus-silent’, and refers to Nikon lenses that use a silent motor to control the autofocus system.
AL
See the aspherical lens.
Albumen print
A type of photographic print invented in 1850 by Frenchman Louis Désiré Blanquart-Evrard (1802-1872). It consists of a sheet of paper coated in egg white (albumen) and salt, then dipped in a light-sensitive silver nitrate solution. The paper, when dried, is overlaid with a glass negative and exposed to the sun. The albumen print was widely used until the late 19th century.
Alternative processes
This term refers to a range of photographic processes, mostly dating from the late 19th and early 20th century, which devotees continue to use for their unique qualities. They include the daguerreotype, gum bichromate, cyanotype, salt print, bromoil, platinum, and palladian processes.
Ambient light
The existing light in a particular scene, which may be sunlight, moonlight or an artificial light already providing illumination. It excludes any light source added by the photographer, such as flash or studio lighting.
Angle of view
A measurement of how much a lens can see of a scene from a particular position, usually measured in degrees. The longer the focal length of the lens, the narrower the angle of view. Zoom lenses have adjustable angles of view.
Antialiasing
A method of smoothing diagonal or curved lines in digital images to avoid a ‘staircase’ or ‘stepped’ appearance (also called ‘jaggies’), caused by the fact that the pixels making up an image are discrete blocks of colour.
Aperture
The opening in the lens that restricts how much light reaches the image sensor. In all but the most basic cameras, the size of the aperture is adjustable. The aperture setting used has an important role to play in both exposure and depth of field.
Aperture priority
Semi-automatic exposure system, where the aperture is set by the photographer. The shutter speed is then set by the camera to suit the light level reading taken by the camera’s own meter.
APO
Abbreviation of apochromatic. This is used to describe Sigma lenses that use super-low dispersion (SLD) lens elements to reduce chromatic aberration.
APS
The initials of the Advanced Photo System, a short-lived film photography format introduced by Kodak and other manufacturers in 1996. The 24mm film was housed in a drop-in cartridge and could be shot in three different formats. It was mainly used in compact cameras, but also a small number of SLRs.
APS-C
This refers to the size of the sensor used in some digital cameras, measuring around 22.5x15mm, and with a 3:2 aspect ratio. It gets its name and dimensions from the APS (Advanced Photo System) Film format, used in its Classic (C) aspect ratio.
Artifacts
Flaws in an image caused by limitations in the recording or manipulation process. Examples include colour and tonal banding, random blotches or a mottled, grainy appearance.
ASA
A method of measuring and specifying film speed, or a film’s sensitivity to light, as devised by the American Standards Association in 1943. It was replaced by the ISO (International Organisation for Standardisation) film speed system in the 1980s. Also, see ISO.
AS and Asp
Abbreviations for a-spherical. See a-spherical lens.
Aspect ratio
The relationship between the width and height of a picture, which describes the proportions of an image format or a photograph. The aspect ratio of most D-SLRs is 3:2, while on most other digital cameras, it’s 4:3.
A-spherical lens
A lens element that has a surface that isn’t perfectly spherical. All camera lenses are made up of a number of individual lenses or elements. Many of these elements are spherical as if cut from a sphere. A-spherical elements are less rounded and are used in wide-angle and wide-aperture lenses to help provide distortion-free images.
Astrophotography
Photography achieved by attaching a camera to a telescope and concerned with recording images of astronomical objects in the night sky such as stars, planets and the moon. Astrophotography can also be used to record astronomical objects invisible to the human eye by using long exposures.
AT-X
Stands for Advanced Technology Extra – the branding used on all current Tokina lenses.
Auto-bracketing
A feature on some cameras that enables you to automatically shoot a sequence of shots of the same scene at slightly different shutter speeds (or aperture settings) from the ‘correct exposure’. This feature can be used if there’s some doubt that the meter reading is accurate for a particular subject. It can also be used to shoot a sequence that’s combined into one high dynamic range image. See HDR. Other auto-bracketing features available on some cameras include automatic flash, ISO or white balance bracketing.
Autochrome
The name of the first colour photography process, invented by French brothers Auguste and Louis Lumière, and patented in 1903. A glass plate was coated in microscopic grains of potato starch, coloured red, green and blue, overlaid with a black-and-white silver halide emulsion. The process was widely used until Kodachrome and Agfacolor films were introduced in the 1930s.
Autofocus
See AF.
Available light
See ambient light.
Avedon, Richard
Avedon (1923-2004) was one of America’s most famous fashion and portrait photographers. He was the chief photographer for Harper’s Bazaar magazine in the 1940s and Vogue from the 1960s. His portraits are famous for their intimacy as well as their stark and minimalist quality.
AWB
Automatic white balance. This is a system that automatically adjusts the colour balance of an image, according to the colour temperature of the light source, to make it look as natural as possible to the human eye.
B
B (Bulb)
The Bulb setting (abbreviated B) on camera shutters is a momentary-action mode that holds shutters open for as long as a photographer depresses the shutter-release button. The Bulb setting is distinct from the shutter’s Time(T) setting, which is an alternate-action mode where the shutter opens when the shutter-release button is pressed and released once and closes when the button is actuated again.
The bulb setting is used on some cameras, including some point-and-shoot cameras, to obtain shutter speeds slower than the minimum offered by the camera otherwise.
Because of the risk of camera movement, the camera is most often mounted on a tripod for the duration of the exposure. While it is generally possible to use the shutter release button on the camera itself, a cable release or electronic remote is often used to further eliminate the risk of shaking the camera during long exposures. The cable releases generally include a locking feature to eliminate the need to keep the button or plunger depressed during extremely long exposures.
The bulb setting is useful for the following types of photographic subjects:
- fireworks at night
- the night sky and celestial objects (see astrophotography)
- lightning
- streets at night (creating streaks from moving cars)
- light painting
Backlighting
An image is backlit when the light source is on the far side of the subject in relation to the camera. It means that there’s more light coming from behind the subject than is directly on the subject itself. It’s often used to separate the subject from the background to make a subject more dramatic, or to make a silhouette.
In photography, a backlight (often the sun) that is about sixteen times more intense than the key light produces a silhouette. A fill flash used with a backlit subject yields more even lighting.
The vertical angle of the backlight can change the effect. A low angle can make the light hit the camera lens, causing a lens flare. A high angle can make the subject’s nose extend out from the mostly vertical shadow of the head, producing a potentially unwanted highlight in the middle of the face.
Backup
A copy of a digital file that’s kept in case of damage to, or loss of, the original digital image.
Ball head
A type of tripod head in which the head mount, which holds the camera, is attached to a ball-and-socket joint. When the socket is tightened using the ball lock knob, it locks the head in place.
Barn doors
Four hinged doors fixed on the front of studio lights. The doors are used to modify the shape and the direction of the light.
Barrel distortion
Barrel distortion is a lens fault or aberration that causes straight, parallel lines in an image to bow outward, and is seen when shooting with wide-angle lenses. The wider the lens, the greater the distortion. The appearance is similar to the effect you’d see if an image was wrapped around a barrel.
It can be corrected using post-capture software.
Beauty dish
A studio lighting device used to give a flattering effect in portrait and fashion photography. It consists of a large circular dish-shaped reflector, usually around 40-50cm in diameter, with a light source in the center. The light usually has an opaque cover so that only the diffused light reflected from the dish reaches the subject.
Beauty Dish example:
The difference when using:
Bellows
A concertinaed tube made of flexible, light-proof material that separates a lens from the camera body. Bellows were first used on very early cameras in the mid-19th century, and are still used on large-format equipment (such as the Ebony view cameras) today. They allow the plane of focus to be adjusted via a swing and tilt mechanism. Bellows are also used instead of extension rings on SLR cameras for making more finely adjustable macro images.
Bit
The basic unit from which any digital piece of data is made. Each bit has a value of either 0 or 1. The sizes of digital files are usually counted in bytes, which are each made up of eight bits.
Bit depth
The number of bits used to record the colour of a single pixel. Digital cameras usually use at least eight bits for each of the red, green, and blue channels, providing a 24-bit depth, and possible 16,700,000 colours. Many D-SLRs offer higher bit depths when setting to record in raw mode.
Blending mode
Blending modes determine how the pixels in a layer interact with the underlying pixels on other layers instead of simply covering them. Some blending modes are much more useful for photo editing than others. Multiply is used to darken an image, and Screen to lighten it; Overlay and Soft Light boost contrast.
Blown out
Bright areas in a photo that are over-exposed are said to be blown out. They won’t hold any detail and will be bleached white.
Bokeh
Derived from the Japanese word for ‘blur’, this term is used to describe the aesthetic quality of the blur in out-of-focus areas of a picture, or the lens creating them. Smooth, circular out-of-focus highlights are a feature of ‘good bokeh.’
Bounce flash
The indirect flash-lighting technique, where the flashgun is angled to bounce off a wall, ceiling, or another reflector. This scatters the illumination, creating a softer lighting effect.
Bounding box
In Photoshop, a rectangular border around a selected part of an image that can be dragged to transform, rotate, scale or move.
Bracketing
A system for increasing the chances of getting the correct exposure by taking a sequence of
pictures with a slightly different exposure setting for each.
Bridge camera
A camera that bridges the gap between compacts and D-SLRs. They are similar in appearance and handling to small D-SLRs, but they have a fixed, usually ‘super zoom’ lens, with some models offering up to 50x optical zoom. Instead of a D-SLR’s optical viewfinder, they have an electronic viewfinder.
Brightness range
This is the difference between the brightness of the brightest part of the subject and the brightness of the darkest part of the subject. Also known as Subject Brightness Range (SBR).
Buffer
Temporary memory used by a digital SLR. The size of the buffer in a camera helps dictate the maximum burst rate and the number of shots per burst.
Burn tool
A tool that can be used to darken parts of an image selectively during digital image manipulation. The tool gets its name (and its hand-shaped icon) from ‘burning- in’, a traditional darkroom process in which parts of a print could be made darker by giving some areas of a print more exposure than others. Also, see Dodge tool.
Burst rate
The continuous shooting speed of a digital camera, which enables a sequence of images to be taken in rapid succession, measured in frames per second (fps). The rate can only be sustained for a certain number of shots.
Butterfly lighting
A technique for lighting portraits achieved by pointing the flash down towards the front of the face and creating a distinctive butterfly-shaped shadow under the nose. A reflector is used to soften the shadow. This technique is also known as ‘Paramount lighting’ after the movie studio’s glamorous portraits from the 1930s.
Byte
The standard unit for measuring the memory capacity of digital storage devices. Each byte can have one of 256 different values, and is equal to eight bits.
C
Cable release
A mechanical or electronic device for firing a camera from a short distance away, without physically pressing the shutter release. It’s often used as a way to minimize vibration when using a slow shutter speed and camera support, such as a tripod.
Calibrator
A device used to standardize the colour and brightness of a computer monitor so that images can be accurately adjusted.
Calotype
One of the earliest photographic processes, announced by William Henry Fox Talbot (1800-1877) in 1841, in which a negative image was recorded on a sheet of translucent paper coated with light-sensitive chemicals. The earliest surviving example is an image of a window at Lacock Abbey, made in 1835. Using the process, multiple positive images could subsequently be produced by contact-printing the negative.
Camera shake
Blurring of the image caused by
movement of the camera during
the exposure. Handheld cameras
are prone to camera shake, and the
fastest available shutter speed
needs to be used to reduce or
eliminate the problem.
Camera trap
A remotely activated camera used
for documenting the behavior of animals
in the wild without the photographer being present.
The camera’s shutter is usually triggered
when an animal’s movement is detected by an
infrared or motion sensor. Cameron, Julia Margaret
Julia Margaret Cameron (1815-1879) was a
British photographer who made portraits
of some of the major figures of the Victorian
period as well as her relatives and
friends. She was one of the first
people to see photography as an
artistic medium open to interpretation,
rather than simply a mechanical process
for recording reality. Her portraits often make a
creative use of soft focus.
Cartridge film
A type of photographic film housed
in a plastic cassette. Because it’s
light-tight, film can be loaded into
a camera in daylight. 126 cartridge
film was introduced by Kodak in
1963, followed by 110 film in 1972.
Two later formats, Disc film and
APS film, used their own specially
designed cartridges.
Catchlight
A white highlight in the eye of the
subject, which is a reflection of the
light source. The shape, size and
intensity of the highlight, as well as
the number of highlights, will vary
depending on the lighting setup.
Centre-weighted
A type of built-in metering system,
provided as an option on some
cameras. Centre-weighted meters
measure light intensity across the
entire image area, but bias the
average in favor of light taken
toward the center of the frame. The
system isn’t foolproof; it’s easier to
predict when it will make an
inappropriate reading than more
sophisticated metering systems.
Channel mixer
A feature in Photoshop that
enables you to adjust the red, green
and blue channels to increase or
decrease colour saturation, or
convert an image to monochrome.
Chiaroscuro
A term that originated in
Renaissance art. It refers to a style
of image that features a strong
contrast between the light and dark
areas of the picture.
Chimping
This is a short form of ‘checking
image preview’. It refers to the act
of looking too frequently at the
image on your camera’s LCD
screen, rather than concentrating
on the subject.
Chromatic aberration
A lens fault common in telephoto
lenses in which different colours of
white light are focused at slightly
different distances, creating ugly
coloured haloes around the edges
of a photographic subject. Software
can remove or reduce the effect.
Chromogenic film
A fine-grain photographic film
that produces black-and-white
images, but is processed using C41
colour chemistry.
Circular polarizer
A type of polarizing filter. Circular
polarizers can be used with modern
cameras without interfering with
the operation of exposure metering
and autofocus systems, unlike
older and cheaper linear polarizers.
Clipping
Clipping occurs when the dark
parts of an image become pure
black or the light parts become
pure white, so that image detail is
lost in these areas. On a histogram,
a clipped shadow or highlight is
indicated by the graph being ‘cut
off’ on the left-hand (shadows) or
right-hand (highlights) side.
Clone Stamp
An image-editing tool that enables
you to replace an area of the image
with pixels taken from elsewhere in
the image (or even another image).
It’s commonly used for removing
blemishes and other unwanted
objects from a picture.
Close-up lens
A filter-like accessory that fits on
the front of the camera lens to
magnify the image. This low-cost
macro accessory can be used on
most types of cameras and lenses.
Close-up lenses come in a variety
of different strengths, usually
measured in dioptres. CMOS
(Complementary Metal Oxide Semiconductor)
This is a type of imaging sensor
used in digital cameras. Located at
the focal plane, it converts the
focused image into an electrical
signal. It’s similar in function to
the CCD sensor.
CMYK
Cyan, magenta, yellow and black
(or ‘key’), the four primary inks
used in commercial colour
printing. CMYK also refers to the
printing process itself.
Collodion process
This is an early technique for
making photographic prints,
invented by Frederick Scott Archer
(1813-1857) in 1851, which used
collodion (cellulose nitrate) to stick
light-sensitive chemicals on the
surface of a glass plate. The plate
was exposed, developed and fixed
while still wet. The process
produced good results and was
used widely until around 1880.
Colour cast
A colour tint in an image, caused
by shooting in a particular kind of
light. Tungsten light causes a
yellow cast, while fluorescent light
causes a green cast. Casts can be
corrected using the camera’s white
balance feature, or at the post-
capture stage.
Colour channels
Every colour you see on a screen is
created by a specific mix of red,
green and blue light, and every
printed colour by a specific
formula of ink colours. In
can be represented and seen as
separate colour channels – RGB for
most digital photos. See Channel
mixer for more on this.
Colour filter array (CFA)
The pattern for red, green, and blue
filters used over the photo sites in
an imaging sensor. Usually, half the
photo sites in a digital camera
(which define pixels) have green
filters, a quarter have red filters,
and quarter have blue filters.
Colour management
An overall system that tries to
ensure that the colours of an image
are displayed and output in exactly
the same way, whatever the device
being used.
Colour profile
Description of how a camera,
printer, monitor or other device
displays or records colour. It
provides a universal way in which
different devices can produce
similar-looking results. This is
sometimes known as an ICC
profile, because the standards are
set down by the ICC (International
Colour Consortium).
Colour negative film
Film on which all original colours
are recorded as their
complementary colours. When the
image is printed on photographic
paper, the colours are again
reversed to their original hue.
Colour negatives have an orange
tint or mask, which helps to
control contrast and improves the
reproduction quality.
Colour reversal film
Film processed to produce a colour
positive image on its transparent
base. Traditionally, images are
mounted in card or plastic mounts.
Also commonly known as slide or
transparency film.
Colour space
The theoretical definition of the
range of colours that can be
displayed by a device.
Colour temperature
All light sources have a
characteristic colour temperature:
artificial (tungsten-filament) lights
are warmer (more orange) than
daylight, which is warm near dawn,
turns cooler (more blue) during the
day, then warms again at nightfall.
Our eyes adjust for colour
temperature much of the time
without our realizing it, so that
colours look pretty consistent.
Digital cameras can make
electronic adjustments using a
white balance system to neutralize
colours. When they get it wrong
(or you use the wrong white
balance setting on your camera),
a colour cast results.
Combination printing
The use of two or more negatives
to make one print. The technique
was first used in the mid-19th
century to overcome exposure
limitations in early photographic
processes, although photographers
such as Oscar Gustave Rejlander
(1813-1875) could use dozens of
images to make one epic scene.
Compact
A type of camera with a shutter
mechanism built into the lens.
Compacts are generally point-and-
shoot designs that are easy to carry
around. Most digital compacts have
built-in zoom lenses.
Complementary colours
Also known as ‘opposite colours’,
these are pairs of colours that
create a strong contrast. On the
traditional colour wheel they are
red/green, yellow/violet and blue/
orange, while the CMYK and RGB
models use red/cyan, green/
magenta and blue/yellow.
Compression
The process of reducing the sizes
of files such as digital images, so
that they use less storage capacity
and are faster to upload and
download. See lossless compression
and lossy compression.
Contact print/sheet
Contact prints are photographic
images made by laying one or more
film negatives on a sheet of
photographic paper, usually under
a sheet of glass, and exposing it to
light. In the traditional wet
darkroom, a contact sheet is
usually the first stage of printing
an image.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Continuous autofocus
This is an autofocus setting in
which the focus is constantly
adjusted until the shutter is
actually fired. It’s especially useful
for moving subjects such as in
wildlife or sports photography,
where it would be unhelpful for the
focus distance to be locked as soon
as it’s initially found.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Continuous lighting
Lighting that remains on
throughout a shoot, as opposed to
the brief burst of illumination
given by flash or strobe lighting.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Contrast range
A measurement of the difference
in brightness between the very
darkest and lightest parts of an
image. See brightness range.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Converging verticals
A term used to describe the effect
of parallel lines getting closer
together, particularly the two sides
of a building, or a section of a
building, when shooting from a low
angle of view.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Crop
To remove unwanted parts of
an image.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Crop factor
Sensors of several different sizes
are used in D-SLRs, and this size
affects the angle of view offered by
a particular lens. The smaller the
sensor, the narrower the angle of
view. The ‘crop factor’ is to convert
the actual focal length of a lens to
the effective focal length (EFL –
see below). The crop factor for Four
Thirds and Micro Four Thirds
models is 2x; the crop factor for
most popular D-SLRs is 1.5x or
1.6x. Full-frame D-SLRs need no
focal length conversion, so they
have a crop factor of 1x.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Cross-processing
Sometimes called ‘X-Pro’, in film
photography this refers to
processing colour negative film in
reversal film (E6) chemicals, or
colour reversal film in negative film
(C41) chemicals. The resulting
colour shifts gave images a
distinctive look. The technique was
once especially popular in fashion
photography. A similar appearance
can be created in Photoshop by
boosting contrast and tweaking
colour channels.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School
The ABC of Photography –
Curves
This powerful Photoshop tool
enables you to adjust the exposure
and contrast of an image. By
altering the shape of the curve,
different areas of tone can be
lightened or darkened by varying
amounts. By altering the curves for
each of the different colour
channels, the colour balance of the
image can also be altered to create
special effects, or simply to correct
for unwanted colour casts.
Elements’ version of Curves, called
Adjust Colour Curves, is more
limited than Photoshop’s Curves.
D
DA
Stands for Digital Auto, which features on a range
of Pentax lenses that (unlike some earlier ranges)
don’t have a manual aperture ring. They have a ‘Quick Shift’
mechanism that enables you to override focus manually, even
when the lens is set to autofocus.
DA*
The premium lens range from Pentax, which Combines
weatherproofing with the advantages of the DA range.
Darkroom
A light-tight room for processing and printing
Traditional photographs. Negatives are loaded
into the processing tank in complete darkness,
while a red/orange safe light can be used at the
printing stage.
Daguerre, Louis
Louis Daguerre (1787-1851) was an artist and
inventor who devised one of the earliest photographic
processes, the daguerreotype, announced in 1839.
It was made by coating a silver-plated copper sheet
with light-sensitive silver iodide, and exposing it in a
camera to create a positive image.
DC
This features on the range of Sigma lenses that
are designed specifically for use with crop-factor
SLRs, and which can’t be used with full- frame models.
Decisive moment
The split-second when all the elements of a photograph
simultaneously come together. The decisive moment is
associated with Cartier-Bresson, who described
photography as “the simultaneous recognition,
in a fraction of a second, of the significance of an
event as well as of a precise organization of forms
which give that event its proper expression.”
Dedicated flashgun
A type of flashgun that’s designed to provide direct
one-way or two-way communication with the
camera. The amount of dedication varies enormously
depending on the flashgun and camera. Increased
dedication tends to provide a more accurate flash
metering, as well as making the flash system easier to
use successfully.
Depth of field
A measure of how much of a picture is in focus, from
the nearest point in the scene to the camera
that looks sharp, to the furthermost point that looks sharp.
Depth of field is dependent on the aperture used, the
distance that the lens is focused at, and the focal
length of the lens.
Depth of field preview
Device found on some digital SLRs that enables you to see the
viewfinder image at the actual aperture you’ll be using for the
exposure. This gives a visual indication as to how much depth of
field there is, and which parts of the resulting picture will be sharp
or blurred. This is necessary because the viewfinder normally
only shows the image as it would appear if the widest aperture
available were used.
Depth of field scale
A scale found on some lens barrels that can be used to work out the
depth of field for particular apertures, and that can be used
for manual focus adjustments to maximize or minimize the depth
of field.
Depth program
A program exposure mode in which the aperture and shutter
speed are set automatically in order to provide the maximum
depth of field, while maintaining a shutter speed that’s
fast enough for hand-held photography. With some cameras,
the different subject distances measured by the
multipoint autofocus system are also taken into account,
and the focus is adjusted to suit.
DG
This refers to the Sigma lens range suitable for full-frame SLRs (but
that can also be used on crop- factor models).
Di
Tamron’s ‘Digitally Integrated’ lenses have a full-size image circle,
so they are suitable for full-frame and crop-factor SLRs.
Di II
Tamron’s second-generation Digitally Integrated lenses are
designed for use on popular crop-factor SLRs, and are not
suitable for full-frame models.
Diaphragm
Another term for the aperture. These are the adjustable blades
that regulate how much light enters the lens and reaches the sensor.
Dialog
A window that pops open when you select certain commands,
usually to give you the opportunity to configure settings or enter
further preferences. In Photoshop and Elements, menu commands
that will open a dialog for further instructions before applying their
effect are usually indicated by an ellipsis (…) after the name, such as
File>Save As… Those without this, such as File>Save, will work
immediately, with no dialog.
Differential focusing
Controlling depth of field to ensure that one element in the picture is
sharp, while others are as out of focus as possible.
Diffraction
Scattering of light caused by deflection at the edges of an
opaque object. Diffraction causes slight fuzziness in the
image when the narrowest apertures are used.
Diffuser
Any material that scatters the light as it passes through it,
Softening the illumination and making
shadows less distinct. Diffusers are commonly used
with artificial light sources. On sunny days, clouds act
as natural diffusers.
Dioptre
Optical measurement used to describe the light-bending
Power of a lens. The dioptre value of a lens is equal to
the number of times that its focal length will
divide into 1000mm. Dioptres are used to measure the
magnification of close-up lenses, and of
viewfinder lenses.
Dioptric correction
The facility provided on some cameras for adjusting the
viewfinder to suit the user’s eyesight. Limited adjustment is
built-in and some cameras permit further modification
with the use of additional dioptre lenses.
Disc film
A short-lived format introduced by Kodak in 1982.
The disc-shaped film, housed in a plastic cartridge,
contained 15 negatives measuring 11×8 mm.
After each exposure, the disc rotated to the next frame.
Poor image quality made it unpopular,
and it was discontinued in 1999.
DNG (Digital Negative)
DNG is a raw file format invented by Adobe and used
by some camera manufacturers. An advantage of
DNG is that, unlike other raw formats, it isn’t specific
to just one camera manufacturer or model, and
it isn’t just a read-only format – you can save your files in DNG
format too. A free DNG converter application available from Adobe at
www.adobe.com/products/dng enables you to convert any raw file
into a DNG.
DO
Diffractive Optics is used on a handful of Canon telephoto lenses.
The technology enables these long lenses to be made smaller and
lighter than equivalents using conventional optical designs.
Dodge tool
A way of lightening selected areas of the image during digital
manipulation. The tool gets its name (and its spoon-shaped icon)
from the traditional darkroom technique of ‘dodging’, where parts
of a print are shielded from exposure and therefore given less
light than other parts. See also Burn tool.
Doughnuts
The name given to the ring-shaped bokeh created by the unique
construction of a mirror lens.
DPI
Dots per inch. Strictly speaking, a measure of the density of dots of
ink that a printer lays down on paper. Compare image resolution
(density of pixels) of a print or on-screen image at a certain size,
measured in pixels per inch.
DPOF
(Digital Print Order Format) A facility available on some digital
cameras that enables users to mark the images from which they wish
to have prints made.
Duotone
A duotone image is one made from two inks (usually black and another
colour), and is often used in printed books to increase the tonal
range of an image. It’s also used by some fine-art photographers to add
subtle colour to black-and-white photographs. A similar appearance
can be achieved in Photoshop by converting a colour image to
greyscale, then choosing Image > Mode > Duotone.
DX
Tokina’s and Nikon’s way of marking lenses that are only
suitable for crop-factor (or APS-C) digital SLRs.
Dynamic range
A term used to describe the range between the lightest and darkest
points in a photograph. The range that can be recorded by a digital camera is relatively small compared with the range that the human eye
can perceive.
Sources: Pixabay, Wikipedia, Susan Wingfield Lamar High School