All cameras from the simplest to the highest of high tech share some basic features.
Lens. The lens is made up of layers of glass which are each shaped to focus incoming light onto a surface used to expose the image.
Light sensitive medium. In digital cameras this is a sensor - which comes in a variety of types but all basically change light into an electrical signal. In film cameras, the exposure takes place on, you guessed it, film.
A variably sized hole call the aperture. Located in the lens, the aperture control is a series of blades which changes the amount of light passing through lens. The aperture's basic unit of measurement for how much light is getting through is the "ƒ Stop." A whole Stop change in aperture lets in either half as much light or twice as much light. On your lens (or in the view finder, or maybe on an LCD menu on your camera) you typically see numbers like ƒ1.8, ƒ2.8, ƒ4, ƒ5.6, ƒ8, ƒ11, ƒ16, and ƒ22. These are whole Stops which, as previously explained, lets in twice as much or half as much light compared to the Stop beside it.
(It should be noted, f1.8 is actually 1/3 of a stop more than f2 which is the actual full stop difference from f2.8 - however more lenes go to f1.8 than f2 as the maximum aperture.)
Learn more about aperture with this video.
A shutter which limits how much time light is allowed to enter your light-tight box. The measurement for the shutter is the "shutter speed," also known as Stops, which is measured in fractions of a second like 1/30th, 1/60th, 1/125th, 1/250th, 1/500th and so on. You can see a little easier how each might vary the exposure by either half as much light, or twice as much. Exposure times can also vary from 1/8000th of a second to several seconds. Some systems can use up to hours of exposure
When hand holding the camera, its important to make sure the shot is not blurry from camera shake. You should have the shutter set to the "same number" as you lens length. For example, if using a 50mm lens, you want a shutter speed of at least 1/60th of a second. If you're using a 135mm lens, 1/125th is okay, but 1/250th would be better. I've found with digital, because most have a multiplier effect (the sensor is smaller than 35mm film, and effectively make the lens 50 per cent longer) you need to set the shutter accordingly. If using a 50mm lens on a digital SLR, I set the shutter to the half stop of 1/90th or faster.
If you don't have enough light for the exposure I recommend a sturdy tripod. If you have a questionable speed, you can try bracing yourself against a post, tree, or other stationary object. I never stop from taking the shot even when I'm doubtful, you never know - you might get a great shot anyways.
Learn more about the shutter with this video.
Light Sensitivity also known as ISO – The actual written standard for ‘measurement of sensitivity to light’ is ISO 5800:2001 (in case you wanted to know.)
One of the ways to think about light sensitivity is that if – in bright daylight with the sun behind you – you set your aperture to f16 you can set both your ISO and shutter speed to ‘about’ 100 (actually 1/100th of a second for the shutter.) And if you set the camera to ISO 400 you can use 1/400 of a second. With old film cameras you had to go to the nearest similar shutter speed – 1/125 and 1/500 in this example. These settings will give you a very close to proper exposure.
Low ISO gives you the best quality in terms of noise or graininess, and that high ISO gives you more latitude for higher shutter speeds. It’s a compromise. With experience and practice you get to know which way and how much you can push either of those settings.
A light tight box. Holding the lens, shutter and exposure medium, the body of the camera keeps light out. On most cameras, the body also holds electronics to control the aperture and shutter.
The meter will help you determine the exposure you need. This is not something you can use on all cameras - particularly very old SLR's and most point-and-shoot style cameras. The meter may be part of the camera's system, but not have any visible meter for the photographer to use. However, most serious cameras do have a display for the meter so you can determine your exposure.
The most important part of the camera is the six inches BEHIND the viewfinder (assuming you use the viewfinder, if you normally look at the LCD on the back of your digital camera that would change to about 18 inches.)
A note about Stops. On modern cameras, there are numbers for additional fractions of a Stop, which can be either 1/2 Stops or 1/3rd Stops. This makes learning your stops a little more complicated but the principal still works.
Almost everything else on modern cameras is a way to control the focus of the lens, the aperture or the shutter speed. On digital cameras there is one last control which is to set the colour temperature. This will be explained later in another lesson.
If you're using a modern digital SLR, or a film SLR with a lot of automation on it, I highly recommend you read your camera's manual closely to find out how to do basic control of: setting the camera to manual exposure, setting the lens aperture, and setting the shutter speed. These three areas are important for getting the most out of these lessons.
If you are using a pocket camera or point-and-shoot style camera, you can set these features on some but not all cameras of this type. If not, you can skip the exposure control lessons and just do the composition lessons.
For some advice on buying your first advanced camera - see this post.