THE SINGLE LENS REFLEX (SLR) CAMERA
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| The Nikon D80 is a popular choice in Digital SLR |
SLRs,
or single-lens-reflex cameras are the choice of most avid
amateurs and professional photographers. The light path for both viewing and taking comes through the lens (TTL), thus there is
virtually no difference between what is seen through the finder
and hot the image ends up, even with close-ups. The light travels
through the lens and hits a mirror inside the camera; this reflects
the light upwards into a pentaprism (a mirror box) which then
travels the light toward the eyepiece viewfinder. The mirrors
are what give the camera the "reflex" name; "single lens" refers
to the fact that one lens is used for gathering light.
The shutter
is contained within the camera body and may be composed of curtains
or blades. Because the shutter is composed of a leading and following
set, very fast shutter speeds (up to 1/8000 second in some models)
can be obtained. (In lens/shutter cameras high speeds are generally
limited to 1/500 second.) Lenses are interchangeable, and cover a
very wide range of focal lengths, giving access to both very wide
and very long telephoto angles of view. Focusing is manual or automatic,
depending upon the model and lenses used.
In each case, the focus is seen in the viewfinder; when combined with
a depth of field preview feature, or when using depth of field indicators
on the fixed focal length lens barrel, the photographer can judge
what will be sharp and unsharp in each image. This is a key advantage
over all other types of cameras.
Virtually every SLR has automatic exposure control; most also allow control over very fine
nuances of exposure through overrides, compensation and other built-in features. Some exposure
control systems are highly sophisticated, relying on computers to do virtual scene and lighting
evaluation. Automation is now tied in with flash exposure as well, a feature that opens up many
new possibilities for creative photography. Many SLRs also offer very high framing rates,
with some high-end models delivering up to 8 frames per second (fps).
In short, the SLR displays the height of technology in photography
today. Innards sport a host of microprocessors, micromotors, and finely-tuned
sensors that literally analyze scenes and subjects, and drive all
the systems that make for easy handling. While automation does
cover many shooting situations, SLRs can also be customized by
the photographer, a key to creative picture control. Buying an SLR
means buying into a system, with all the lenses, accessories and options
that open the door to virtually every type of image and subject matter.
This full-system approach is what puts the SLR into a class unto
itself.
The
wide appeal of the SLR means that there are many models from
which to choose. Options range from SLRs that are like point
and shoot camera with interchangeable lenses to highly sophisticated
instruments that offer superb automation coupled with the capability
of photographer customization to virtually every shooting scenario.
When you purchase a SLR you join a system of lenses and accessories
for everything from fully automated flash photography used by professionals
to special gear for close-up and special interest work.
There
are a number of options to explore. In many cases your budget will
help make the choice, but don't base your buying decision on price
alone. If you can get all the features you want for a few extra dollars
you won't regret it, as you probably will be working with the camera
for a very long time. Many photographers limit their choices, only
to find that they want to get a higher-featured camera later as their
experience and understanding of photography expands.
Exposure
Modes: An exposure mode is a way of setting up the camera's
exposure system. Most every SLR today offers automatic exposure (the
camera sets aperture and shutter speed for you). The most important
options within auto exposure include Program (the camera makes all
the exposure decisions); aperture-priority (you set the aperture and
the camera selects a shutter speed); and shutter priority (you set
the shutter speed and the camera sets the aperture for you). Be sure
to get a camera that reads out the aperture and shutter speed values
in the viewfinder. This is essential information for creative photography.
Some cameras also offer Picture modes, pre-programmed solutions to
exposure calculations. Portrait mode, for example, sets a wide aperture
for minimum depth of field; Action mode selects the fastest possible
shutter speed for freezing motion; and Landscape mode sets a narrow
aperture for maximum depth of field. If you're just learning about
photography these modes can help you maximize your photographs. If
you know how to make settings that accomplish the same thing you don't
need these modes.
Exposure
Metering Patterns: Many SLRs today have very sophisticated
metering systems that analyze a scene and make calculations based
on algorithms that have been pre-programmed into the camera. This
may be called Matrix, Evaluative or Intelligent metering, or something
to that effect. Other options include center-weighted and spot metering.
Those who have more experience or who want to expand their photographic
knowledge should look for the full host of metering system options.
If you don't want to bother with exposure calculations you won't need
a spot metering option.
Manual
Focus and Exposure: Some teachers feel that students should
begin with a manual focus and exposure camera to learn the basics
of photography. These cameras have exposure systems, but they suggest,
rather than set actual exposures. The user must set them him or herself.
The same goes with focus. This is one approach that is not universally
accepted. If this appeals to you there are a number of excellent manual
focus and exposure cameras on the market aimed at the student and
those who want to learn this way. These cameras are usually less expensive
and generally have less options in lenses and accessories.
Focusing: Most SLRs work with autofocusing systems.
Some work with a single focus spot in the center of the viewfinder.
This means that the subject focus must be set by placing the centered
autofocus detector over the subject. The composition can be changed
via use of an autofocus lock button that holds focus even if the subject
is off center in the frame. More sophisticated SLRs have multi-autofocus
detectors in the viewfinder. The system usually prioritizes the subject
closest to the photographer. Some SLRs have autofocusing systems that
follow moving subjects well or predict motion to help maintain focus
in action sequences. Most every SLR with autofocus has both single
and servo autofocus modes. Single means that the camera will not allow
exposure until focus has been confirmed; servo is used with moving
subjects. The former is best for portraits and still life photography
while the latter is used for wildlife and sports work. The speed of
autofocus is key and some high-end cameras offer autofocus tracking
as fast as 6 frames per second, or faster with certain accessories
and lenses.
Framing Rates: Framing rate means the number of frames-per-second
the camera will fire. Framing rates range from 1 frame per second
to as high as eight frames per second. If you photograph sports or
wildlife on the wing the higher framing rates are preferred.
Customization: While the SLR out of the box is pretty impressive, some cameras allow
you to customize the settings to your own way of working. This have
on board microprocessors that can be programmed through push-button
menus on the camera. Some even allow patching to a computer with even
more customization options, or remote operation of the camera. This
customization can be applied to the way the camera focuses, exposes
and even how certain buttons and dials on the camera perform...
Ease of Downloading: The reason you use a digicam
is for instant digital images without conversion from film. To work
on and send or share the image you have to get it into a computer.
Some digicams allow for a direct patch to the computer via parallel,
serial or USB connection, or even use a SCSI adapter. Some even offer
infrared download. Perhaps the easiest method is to use a memory card
and use a card reader, a drive into which you put the memory card
to patch directly to the computer. This eliminates the need for direct
wiring between camera and computer.
User Input: Perhaps the most important aspect of
SLR choice is the way the camera is designed for user input. Because
an SLR is a creative, spontaneous picture taking machine, the user
should be able to work nimbly with all controls. For example, many
SLRs allow for exposure compensation, a way to override the camera-recommended
exposure for a creative or interpretive touch. Some cameras use handy
dials for this input, while others may require more extensive workarounds.
This idea extends to viewfinder information. While too crowded a finder
will be confusing, the photographer should have all the information
required at eye level, rather than having to looking at on-camera
dials or a body mounted LCD.
Full System Approach: An SLR body can be an investment. Be sure
to explore the system of lenses, flash, accessories and other features
that surround it. When you buy an SLR you buy into that system as
well.
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