Photography Tutorials
How the camera works
Types of camera
Exposure
Aperture and depth of field
Focus sharpness shake and blur |
How the camera works
Even if you just want to “point and shoot” with your camera, having a basic knowledge of how the camera works can greatly improve your photographs. So, here I aim to give, in the simplest terms possible, an overview of how they work, types of camera as well as their strengths and drawbacks.
Film and digital Cameras have several things in common, they both have a lens to focus the image onto the film or sensor, an aperture (hole through which light passes), and of course the film or sensor which records the image itself.
A major difference is that while all film cameras need to have a shutter, most digital cameras do not. This is because whilst film creates an instant record of the image it is exposed to, the sensor in a digital camera simply sends a signal to the cameras on board processor which converts it to a file and stores it on a memory card. Exposure time is measured electronically this means that a digital camera does not always need to have moving parts. |
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The lens refracts the light into a different plane making it possible to project a smaller image onto the camera’s film or sensor. When we say lens what we really refer to is a group of lenses in one unit, especially where zoom lenses are concerned.
A lens has a focal length referred to in millimetres and there are two main types, fixed and zoom. Most compacts these days will have a zoom lens, all you really need to know at this stage is that the lower the number in millimetres, the wider the angle of the shot (the more you can see in the picture). As you zoom in the focal length increases and the angle of view narrows. So, the larger the range in focal length the more theoretical possibilities for framing a shot or getting closer when you zoom. Zooming does, however, lower depth of field, more on that later.
The aperture in all cameras is variable, so you can (or the camera automatically will) make the little hole bigger or smaller. Its size is measured in f-numbers - f1 f8 f16 f32 etc. The main thing to remember here, which can seem rather confusing at first is that the LARGER the f-number, the SMALLER the aperture. In other words, f32 would be a rather tiny hole, and f1.8 would be a really big one. The size of the aperture is important since the smaller it is the less light it lets in. This has a lot of implications for taking photos in low light if you can't use a flash. It is also important because of its effect on depth of field, (why is depth of field so important? Later!)
The sensor or film, as we have mentioned, records the image. There is a simple rule here, bigger IS better, and there is a simple misconception to clear up here, that DOESN’T mean the number of megapixels!! Keeping it simple, a larger sensor with fewer megapixels will produce a far better image for a number of reasons than a small one with more (my Eos 20d has 8.2 megapixels, less than a lot of mobile phones these days, but they will never produce an image good enough to pass quality control at a photo agency, the 20d does). So, don’t just let someone sell you a camera because it has 12 million pixels in it, when the one with 8 or even 6 million may do a better job. Try to buy the one with the largest sensor.
With film this also holds true, medium and large format film will produce better images than 35mm but 35mm is much more convenient so that’s what became the standard.
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