Digital photography jargon
Digital photography jardon
D is for....
Depth of field
The distance at which a lens is focused is called the focal plane. All
subjects exactly at this distance will be brought to sharp focus on
the image sensor.
in front of, or behind the focal plane will be progressively rendered
more and more out of focus. (see circle of confusion)
the point will be reached where the out of focus areas will be
visually evident when viewing the final enlarged image.
near and far sharpness limits define the depth of field.
factors determine whether this region is shallow (only subjects close
to the focal plane are acceptably sharp) or deep (subjects from a
long way either side of the focal plane are acceptably sharp)
of subject to the lens
any given lens, aperture, focal length and image sensor size combination
– there exists a focussing distance at which the depth of field is
greatest – known as the hyperfocal
distance – normally all image subjects from half this distance to
infinity will be rendered acceptably sharp.
a more detailed explanation see
of field explained
creative control of your photos
Dslr– stands for Digital single lens reflex camera.
Digital (and film) reflex cameras enable the photographer to view the image that will be captured via an optical viewfinder. The image in the viewfinder being directed there via a mirror system mounted in front of the image sensor – hence the the term “reflex” as the view is a reflection from the mirror.
Dslrs are growing in popularity by photography enthusiasts as the technology develops and prices fall.
Outlined below are two lists of pros and cons – the first weighing the advantages / disadvantages of Dslr with traditional film cameras, and the second compares Dslrs with digital compact cameras.
vs Film slr
per photo – once purchased a memory card may be used and then
erased almost indefinitely dramatically reducing cost per photo compared to traditional film.
review or even live preview – The image taken (or to be taken) can
be instantly assessed on the camera's l.c.d display and therefore
checked for exposure, composition and sharpness. Thus enabling the
photographer to make appropriate adjustments to camera settings or composition
prior to continuing.
process – Digital post process does not require a dark room or
expensive and potentially hazardous chemicals. Far
more photographers are therefore able to take control of the post processing of their
images. (Although with a scanner, film negatives can also be
Sensitivity – With a film camera the light sensitivity of the film
(known as the “speed”) has to be predetermined and cannot be
changed from one frame to the next within a roll of film. Dslrs
enable a wide range of ISO sensitivity (nowadays to quite high levels
at acceptable noise
levels). Thus giving much greater flexibility over exposure control
on a frame by frame basis – particularly relevent to low light photography
size – Generally the higher the format (ie film or sensor) size,
the greater the potential for high image quality. The cost of
production for large image sensors increases exponentially with size.
The cost of “full frame” dslrs is therefore still prohibitive for
most consumers, whilst true medium format digital cameras, although
available, can typically cost tens of thousands of dollars! Having
said this, for most photography enthusiasts, the image quality from
modern dslrs acceptable.
contamination – unlike with a film camera where any dust that gets
into the camera body will almost certainly advance with the film and
thus be cleared – with a digital camera there is the potential that
dust contamination may actually stay on the image sensor and affect
all subsequent shots. This is exacerbated by the fact that the
electro static charge on the image sensor will actually attract dust. Most
recent dslr models incorporate some form of sensor cleaning system to
help deal with the problem and it is also possible to fix any
blemishes during post processing.
- Power supply. Digital
cameras are dependant upon electric power from a battery – whereas
mechanical film cameras have no such dependency.
vs compact camera
- Image Quality - Having a
larger image sensor size means image quality is generally higher –
especially at higher ISO levels
- Interchangeable lenses - The
camera is not limited to having a fixed lens – meaning high quality
lenses best suited to a specific purpose may be used.
- D.o.f. - The
larger image sensor enables greater control over depth of field –
particularly for shallow depth of field effects favoured by portrait
- Viewfinder - An
optical viewfinder gives a clearer and more accurate view than an
electronic viewfinder and enables a faster auto-focusing system to be
- Response time - Often
dslrs respond to the shutter button more rapidly and have faster burst rates for continuous shooting.
- Cost - Generally
higher cost – especially when the cost of the detachable lenses are
taken into account – with these sometimes costing more than the
– the mirror system and the longer focal length lens require the
cameras to be physically more heavy and bulky which can result in the
cameras being less convenient to carry – this can be a major issue
for travel photography or when hiking long distances or when more
discretion is desirable.
- Dust - Dslrs
have a greater tendency to dust getting on the sensor than compact
cameras as the process of changing the detachable lens leaves the
image sensor vulnerable to contamination.
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Depth of field explained
Take creative control of your photos
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