35 mm SLR Cameras
The Camera
This
camera is one of the most highly developed of all cameras; the digital SLR is
based on the camera. The basic idea is
using a hinged mirror to reflect the image formed by the camera lens onto a
viewing screen, until just before the moment of exposure. In a digital SLR the sensor displays the
image on a screen until just before the data is saved to the memory.
The
SLR viewfinder system uses a mirror to turn the image the right way up and a
pentaprism (basically a 5 sided block of glass, silvered on 3 faces) to correct
the left to right reversal. The
pentaprism also offers a compact, but comfortable long optical path between the
screen and the eyepiece, which are really only an inch or so apart. This reduces eyestrain and the need for
complicated wide-angled eyepiece optics.
With the SLR there is a wide selection of interchangeable lens, focusing
screens and viewfinders.
The greatest single
advantage of the SLR camera is total absence of parallax error. You can see exactly what the lens will place
on the film, the precise distance focused and by stopping down the lens, the
limits of depth of field and as lens are interchanged the new field of view is
automatically visible on the screen. The
camera can be attached to a telescope or microscope or be fitted with diffusers
and masks over the lenses and you are still able to see the precise image the
lens will produce. The SLR camera also
has solid state through the lens metering, zoom lens and motor drives. There is an ever-widening equipment system
built around the SLR camera.
A
basic SLR camera consists of a lens and a body, which incorporates a
viewfinder, film speed dial, shutter release, film advance lever, exposure
counter, rewind knob, rewind release button, mirror, focusing screen,
pentaprism, and built in through the lens metering system.
Operation of the 35 mm
SLR CAMERA
1.
Set the ISO number on the Film speed dial
usually on the shutter speed mounting.
2.
Look through the viewfinder, turn
focusing ring on lens barrel until important subject material in view appears
sharp.
3.
Select appropriate shutter sped or
aperture according to visual requirements, i.e. to stop or accentuate movement,
or to increase or decrease depth of field.
4.
Select mid tone grey of subject avoiding
incorrect readings caused by very dark or very light areas.
5.
Adjust either shutter speed or aperture
until 'floating' indicator needle in viewfinder is centered between the plus
and minus indicators. (Some cameras will have lights rather than a needle –
green light is correct). The camera is
now set to correct exposure.
6.
The picture area covered corresponds to
the edge of the viewfinder frame.
7.
Check focus, compose image and gently release
the shutter, then wind lever through to next frame.
