Slr camera how does it work

What kind of settings do I adjust? Which lenses do I choose for my SLR camera? When do I choose an SLR camera? View all SLR cameras. What is the difference between all image sensors? What do the settings mean on my camera? View all lenses for SLR cameras. Did this help you? Yes No. How can we improve this page?

We only use your feedback to improve the website, we won't respond. Submit your feedback. Thanks for your feedback. Article by:. More advice about SLR cameras. Compare mirrorless cameras to SLR cameras. More help with your choice of a camera. In a zoom lens , you can move different lens elements back and forth. By changing the distance between particular lenses, you can adjust the magnification power -- the focal length -- of the lens as a whole.

The chemical component in a traditional camera is film. Essentially, when you expose film to a real image , it makes a chemical record of the pattern of light. It does this with a collection of tiny light-sensitive grains, spread out in a chemical suspension on a strip of plastic. When exposed to light, the grains undergo a chemical reaction. Once the roll is finished, the film is developed -- it is exposed to other chemicals, which react with the light-sensitive grains.

In black and white film, the developer chemicals darken the grains that were exposed to light. This produces a negative, where lighter areas appear darker and darker areas appear lighter, which is then converted into a positive image in printing.

Color film has three different layers of light-sensitive materials, which respond, in turn, to red, green and blue. When the film is developed, these layers are exposed to chemicals that dye the layers of film.

When you overlay the color information from all three layers, you get a full-color negative. For an in-depth description of this entire process, check out How Photographic Film Works. So far, we've looked at the basic idea of photography -- you create a real image with a converging lens, and you record the light pattern of this real image on a layer of light-sensitive material.

Conceptually, this is all that's involved in taking a picture. But to capture a clear image, you have to carefully control how everything comes together. Obviously, if you were to lay a piece of film on the ground and focus a real image onto it with a converging lens, you wouldn't get any kind of usable picture.

Out in the open, every grain in the film would be completely exposed to light. And without any contrasting unexposed areas, there's no picture. To capture an image, you have to keep the film in complete darkness until it's time to take the picture. Then, when you want to record an image, you let some light in. At its most basic level, this is all the body of a camera is -- a sealed box with a shutter that opens and closes between the lens and film.

In fact, the term camera is shortened from camera obscura , literally "dark room" in Latin. For the picture to come out right, you have to precisely control how much light hits the film.

If you let too much light in, too many grains will react, and the picture will appear washed out. If you don't let enough light hit the film, too few grains will react, and the picture will be too dark.

In the next section, we'll look at the different camera mechanisms that let you adjust the exposure. As it turns out, the term photography describes the photographic process quite accurately. Sir John Herschel, a 19th century astronomer and one of the first photographers, came up with the term in The term is a combination of two Greek words -- photos meaning light and graphein meaning writing or drawing.

The term camera comes from camera obscura , Latin for "dark room. A traditional camera obscura was a dark room with light shining through a lens or tiny hole in the wall. Light passed through the hole, forming an upside-down real image on the opposite wall. This effect was very popular with artists, scientists and curious spectators. In the last section, we saw that you need to carefully control the film's exposure to light, or your picture will come out too dark or too bright.

So how do you adjust this exposure level? You have to consider two major factors:. To increase or decrease the amount of light passing through the lens, you have to change the size of the aperture -- the lens opening.

This is the job of the iris diaphragm , a series of overlapping metal plates that can fold in on each other or expand out. Essentially, this mechanism works the same way as the iris in your eye -- it opens or closes in a circle, to shrink or expand the diameter of the lens.

When the lens is smaller, it captures less light, and when it is larger, it captures more light. The length of exposure is determined by the shutter speed. Most SLR cameras use a focal plane shutter. This mechanism is very simple -- it basically consists of two "curtains" between the lens and the film. Before you take a picture, the first curtain is closed, so the film won't be exposed to light. When you take the picture, this curtain slides open. After a certain amount of time, the second curtain slides in from the other side, to stop the exposure.

When you click the camera's shutter release, the first curtain slides open, exposing the film. After a certain amount of time, the second shutter slides closed, ending the exposure. The time delay is controlled by the camera's shutter speed knob. This simple action is controlled by a complex mass of gears, switches and springs, like you might find inside a watch.

When you hit the shutter button , it releases a lever, which sets several gears in motion. You can tighten or loosen some of the springs by turning the shutter speed knob. This adjusts the gear mechanism, increasing or decreasing the delay between the first curtain opening and the second curtain closing. When you set the knob to a very slow shutter speed, the shutter is open for a very long time. When you set the knob to a very high speed, the second curtain follows directly behind the first curtain, so only a tiny slit of the film frame is exposed at any one time.

The ideal exposure depends on the size of the light-sensitive grains in the film. A larger grain is more likely to absorb light photons than a smaller grain.

The size of the grains is indicated by a film's speed , which is printed on the canister. Different film speeds are suited to different types of photography -- ISO film, for example, is optimal for shots in bright sunlight, while film should only be used in relatively low light.

As you can see, there's a lot involved in getting the exposure right -- you have to balance film speed, aperture size and shutter speed to fit the light level in your shot.

Manual SLR cameras have a built-in light meter to help you do this. The main component of the light meter is a panel of semi-conductor light sensors that are sensitive to light energy. These sensors express this light energy as electrical energy, which the light meter system interprets based on the film and shutter speed. Now, let's see how an SLR camera body directs the real image to the viewfinder before you take the shot, and then directs it to the film when you press the shutter button.

There are two types of consumer film cameras on the market -- SLR cameras and " point-and-shoot " cameras. The main difference is how the photographer sees the scene. In a point-and-shoot camera, the viewfinder is a simple window through the body of the camera. You don't see the real image formed by the camera lens, but you get a rough idea of what is in view. In an SLR camera, you see the actual real image that the film will see. If you take the lens off of an SLR camera and look inside, you'll see how this works.

The camera has a slanted mirror positioned between the shutter and the lens, with a piece of translucent glass and a prism positioned above it. This configuration works like a periscope -- the real image bounces off the lower mirror on to the translucent glass, which serves as a projection screen.

The prism's job is to flip the image on the screen, so it appears right side up again, and redirect it on to the viewfinder window. When you click the shutter button, the camera quickly switches the mirror out of the way, so the image is directed at the exposed film.

The mirror is connected to the shutter timer system, so it stays open as long as the shutter is open. This is why the viewfinder is suddenly blacked out when you take a picture. In this sort of camera, the mirror and the translucent screen are set up so they present the real image exactly as it will appear on the film.

The advantage of this design is that you can adjust the focus and compose the scene so you get exactly the picture you want. For this reason, professional photographers typically use SLR cameras. These days, most SLR cameras are built with both manual and automatic controls, and most point-and-shoot cameras are fully automatic. Conceptually, automatic cameras are pretty much the same as fully manual models, but everything is controlled by a central microprocessor instead of the user.

The central microprocessor receives information from the autofocus system and the light meter. Then it activates several small motors, which adjust the lens and open and close the aperture. In modern cameras, this a pretty advanced computer system. In the next section, we'll look at the other end of the spectrum -- a camera design with no complex machinery, no lens and barely any moving parts. As we've seen in this article, even the most basic, completely manual SLR is a complex, intricate machine.

If the image you see through the viewfinder is not exactly the same as the image on the recording medium as in viewfinder cameras , the composition of the resulting photograph may be noticeably different to what you expected. The SLR camera makes sure this doesn't happen. SLR cameras also work well with different lenses. Since you are seeing exactly what the lens sees, you can swap lenses as required and always be confident of what you are capturing.

These disadvantages do not normally present a major concern.