How The SLR Camera
Works
Lesson 2
by Brian D. Ratty
Pictures and Text Copyright© 2005 By Media West Home
Video
There's one thing that happens to me all the time. I'll be out
shooting somewhere and an amateur photographer will walk over and start a conversation
that goes something like this: "Oh, I see you're using a Nikon...I've got a
Minolta...it takes pretty good pictures...but do you think the Nikon is better?" And
he always seems a little disappointed with the answer; a Nikon doesn't take a better
picture than a Minolta, a Canon doesn't take a better picture than a Ricoh or Pentax or
Olympus - they're all equally good. The point is, cameras don't take pictures, people do.
Don't get me wrong. Some of the technological advancements in modern SLR's, made possible
by computer aided design and micro electronics, are really incredible. They really can
take a lot of the guesswork out of your photography. For now let's forget all that because
I want you to think of the camera as just a basic tool. Remember, it doesn't take the
pictures, you do.
A modern SLR camera, film or digital, operates on the very same basic principles as the earliest pinhole cameras, and, for that matter, any other cameras ever made.
I think it helps to think of any camera as a light-tight box with a hole in it. The hole allows a certain amount of light to enter the box for a certain amount of time so that it can expose, or create an image, on the light-sensitive medium we call film or CCD unit. But before that happens, the light is organized, or "focused", by the lens. So let's start with the lens. The lens is basically a metal barrel which contains several glass elements arranged in groups.
These elements gather light reflected from the scene you're photographing, focus that light, and deliver it to the surface of the film, where it can form the sharpest possible image. The barrel of the lens contains a focusing ring which allows you to focus on objects near and far; from less than two feet away to infinity, for example. When you turn the focusing ring you are actually moving the glass elements inside the barrel in and out, varying the distance between the lens and the film. One of the real advantages of the SLR is that the image you see in your viewfinder is exactly the same image that the lens sees. When light enters the lens, it's reflected by a mirror up through a prism and out to your eye. And it doesn't matter which f-stop, or aperture, you've chosen for your final picture, since the image you see in the viewfinder is always at the widest possible aperture of the lens. This makes it easier for you to focus and compose because the image you're seeing is as bright as possible. When you press the shutter release to make an exposure you trigger a whole series of events which happen at an amazing speed.
First, the lens aperture closes down to the f-stop you've selected. Second, the mirror swings up out of the way so that the light can reach the film, temporarily blocking your view. Third, the shutter opens for the amount of time you've selected, and the film is exposed. Fourth, the mirror swings back down, allowing you to see through the viewfinder again. Fifth, your lens aperture returns to wide open. You're ready to focus for your next shot. This general concept of how the SLR camera works is the same for both film type cameras and digital cameras. You'll notice I mentioned f-stops and shutter speeds, probably the most confusing concepts for any photographer who's just starting out. I'll take the mystery out of these concepts in "F-stops and Shutter Speeds".
|
||||||||||||
 |
 |
 |
