WHAT IS SLR?
>Could sombody please explain, in 'english', what makes the 35mm SLR
>unique as compared to all other 35mm's.
> Thanks
> ~Lena~
I'm sorry Lena, nobody's actually answering your question are they?
Let me try:
SLR stands for Single Lens Reflex.
It's a technology which addresses the problem of how to SEE that the camera
is correctly focused on the subject.
'Reflex' means when a beam of light (ie an image) is bent, turned or
reflected backwards or around.
Inside that bulge on top of your camera is a pyramid shaped piece of glass
called a prism.
The picture that your camera lens sees in front of you 'shines' into the
lens, as a beam of light, is turned upside down by the lens, bounces off an
angled mirror inside the camera behind the lens and is shined up into the
prism, which turns the beam around and right way up (ie, reflexes it) and
beams it back out again through the viewfinder you look through, into your
eye. So by a combination of the mirror and the prism, you are seeing
straight through the camera lens, kind of like a submarine periscope upside
down. If the lens is out of focus, you can see it's out of focus because you
are looking through it via the prism and the mirror.
You have to have this mirror and prism arrangement because without it you
wouldn't be able to see directly through the lens from behind the camera
because the film and the shutter would be in the way.
Older cameras had TWO lenses. One to focus the picture onto the film, and
the other to reflect the image into the mirror and up into your viewfinder.
They were called TLR's (TWIN Lens Reflexes) Both lenses moved together so
that when the one you looked through showed a focused image, you knew that
the one lined up on the film would also be in focus.
The SINGLE Lens Reflex camera was invented by hinging the mirror so it could
be automatically flipped up out of the way so that the image could fall
directly on the film at the moment you press the shutter (without the mirror
being in the way). The function of the prism in an SLR is to turn the image
right way up and help to focus and frame it neatly in the viewfinder.
Modern cameras also have a lot of light sensors and electronics stuff
attached to the prism to help with exposure metering.
Many photographers still prefer the old TLR as there is no moveable mirror
to cause vibration that might blur the image, although the distance between
the two lenses causes problems with close-up work as you have to compensate
for parallax error.
Another earlier system of focusing was called Rangefinding, but I won't go
into that.
SLR cameras began to replace TLR and Rangefinder cameras as the most popular
serious cameras in the mid to late 1950's. Nikon were really the first
company to make good SLR cameras which is why almost every single
professional photographer in the world was using a Nikon between 1960 and
1985.
Nikon lost their top place in the professional market after that because
other manufacturers started making autofocus cameras, and Nikon didn't,
wouldn't or couldn't make one for a long time. ('pride cometh before a
fall...')
This has nothing to do with SLR though - Even with Autofocus, you still need
to be able to see exactly what the camera lens is seeing, and check that the
part you want is in focus.
SLR eliminated the TLR problem of parallax error, was more aesthetically
satisfying, technically reassuring and fun to use than rangefinders and also
made cameras slightly smaller, therefore more portable, and slightly easier
to use.
This has been hard to explain in words. You're better off looking at an
illustration of the principle in any good camera book.
Sincerely,
Tube
