Camera for Dummies: Basics

Camera:A boxlike device for holding a film or plate sensitive to light, having an aperture controlled by a shutter that, when opened, admits light enabling an object to be focused, usually by means of a lens, on the film or plate, thereby producing a photographic image.
That's what a Camera is according to Dictionary.com. But believe me it's much simpler than that. :)

To understand the how a camera works lets see how the oldest cameras were designed. The oldest type of cameras were the pin-hole cameras.
Lets create a pinhole camera:
1. Take a sheet of paper and make a hole in it. Diameter can be around 0.5-1 mm not more.
2. Select a wall on which the light is coming almost perpendicularly.

3. Now you need to find out "the distance". This is the distance between wall and the camera (i.e. the sheet of paper) that will expose/create the image on the wall. To to this hold your camera about 1 cm away from the wall and move it away from the wall till you see the picture on the wall.
When you see the image, you have your camera !

Of course you'll say where is the photo ?! Well, it's on the wall, if you want to make it permanent you need a wall that can capture it. Now no one has discovered a wall like this so far but once up on a time someone put some silver dust on surface of something. Knowingly or unknowingly he managed to let some light on this surface. It turned out that the image represented by that light was imprinted on it. Thus was invented silver screen. After lotsa ppl put lotsa thought into this invention, today we have the "camera film".
So to complete our pinhole camera all we gotta do is replace the wall with this film !

Of course you have to ensure that no other light other than the one from your pinhole reaches this film coz then image will be distored.
So what do we do? Instead of just using a single sheet of paper we use a box. With a hole in one side of it and the film on the opposite side. All other sides are covered so the light come only from the hole onto the film, thus capturing the image we want and not something else. So do we have our camera now ??

Not just yet, there still the question how long do I have to expose the film to the light? We know the films are sensitive to the light, Unfortunately if you expose them to little light for a long time, it'll still have the same effect as exposing lots of light for a short duration. So what do we do ? Well, we put some mechanism to control how long the film is exposed to the light.

For the purpose of this explanation we'll use a very crude mechanism to control the exposure time. Take a sheet of paper and cover the hole with it so no light passes through. Now lets say we know that given the amount of light around we need to expose the film for one full second (in practice it's MUCH lesser time), so put the film on the opposite wall of the hole, remove the sheet of paper covering the hole and put it back after one second. Your own little camera is ready.

Now lets look back at what we've done and get introduced to some technical jargon.

• First we created hole in one wall of the box: This is your lens. In practice you'll use an optical lens made of glass.
• Say the diameter of our hole is about 1mm: This is your aperture. In practice the aperture is measured in terms of f-stop instead of mm.
• Then we put a film on the opposite wall: This your film. :)
• We also ensured that the distance between our lens and the film is such that the image is clear (technical term is "image/subject is in focus"): This distance is the focal length of your lens.
• We used a sheet of paper to control the exposure time: This is your shutter.
• Using this shutter we allowed the light to pass through the aperture/lens for 1 second: This is your shutter speed. The longer we allow the light to pass the faster the shutter speed and vise-versa.

The basic principle-of/thing-about photography is to control the amount of light you allow to reach the film. This will ensure that you see the image on the film. Technically this is called controlling the exposure. If you let less than required amount of light to pass the photo will be under-exposed. There are 2 basic ways of controlling exposure:
1. The aperture size: Diameter of the hole through which the light passes.
2. The shutter speed: Duration for which the shutter is kept open to allow the light to pass through the aperture.
In the next artical on aperture we look what can one do with aperture and what will be the side-effects.