University of Sheffield Photo Soc

The Camera

In order to take good photographs, it is essential to know how your camera works. Recently, point and shoot cameras have made it easy for people with little or no knowledge of how the camera works to take photographs. Photographs taken with these cameras often appear mediocre when compared to photographs seen in magazines etc. You may think that this is due to the large amounts of money professional photographers spend on equipment; but this is only partially true. What they have that is far more important is a good knowledge of how to use their equipment to get the best out of it.
However, a point and shoot camera offers very little in the way of creativity since you have no control over variables such as aperture and shutter speed (explained later). Also the quality of the lens will be inferior compared to that of an SLR, and this has a surprisingly large effect on the photo. You still retain control over the composition of your pictures so you may want to take a look at the composition pages. However, if you want to take better pictures and improve your knowledge of photography, the best place to start is with a SLR camera.
But what is an SLR, I hear you cry? It stands for single lense reflex, which means that inside the camera there is a moving mirror. This reflects light towards the viewfinder, so what you see down the viewfinder in an SLR camera is exactly what the photo will look like. In the case of digital SLR cameras, they are abbreviated to DSLRs.
Behind this is the shutter, which protects the film/sensor from light until the correct moment. These are both shown in the diagram below:

DOF - Shallow

Image adapted from How Stuff Works

Also shown is the splitter. In a manual focus camera this helps with focusing: the image is split into 2 in the centre, and you focus by lining the 2 halves up.
While the basics of the camera are the same between film and digital, clearly they are not identical. DSLRs are considerably more expensive to buy, even second hand. However you do get all the advantages of digital: instant feedback on images, able to take many more photos in one go, and photos do not have to be developed and scanned. However, film SLR’s have their own advantages: they are much cheaper (a good camera and lense can be bought for less than £50 second hand compared to over £200 for a similar DSLR), they lack the confusing menu and button systems that plague DSLRs, and you put a lot more thought into photos beforehand when you can’t immediately see the results.

What Do All These Numbers Mean?

If you take a look at your SLR/DSLR camera you will see several dials, all covered in numbers. These relate to the various different settings your camera has. When you are starting off, these numbers can be a bit daunting and/or confusing so this section will hopefully go some way to making things clearer.

Shutter Speed

This changes how fast the shutter shuts after opening, therefore changing how long the film/sensor is exposed to light. The dial that sets the shutter speed is usually on top of the camera, on the right hand side, next to the shutter button. On some film cameras it may be on the front of the body, where the lens attaches to the body.
The numbers on the camera that refer to the shutter speed are given as reciprocals, i.e. 125 means 1/125th of a second and 1000 means 1/1000th of a second. The numbers in a different colour at the other end of the scale refer to whole seconds (usually 1, 2, 4 and 8).
The number 125 may be high-lighted. This is meant as a guide to you, for if you are holding the camera yourself to take photographs, having a shutter speed longer than about 1/125 will probably result in the photograph being blurred. If you need to use longer shutter speeds and retain crisp images you should use a tripod to keep the camera steady.
The more light there is available the shorter the shutter speed you can use.
You may want to blur your picture on purpose to give an impression of speed. If you pan with the camera, that is follow the object you want to capture with the camera, and press the shutter button as the object passes you, the object will be crisp whilst the background will be blurred.
There may be times when you want to leave the shutter open for long periods of time. For example, to capture the movement of the stars across the night sky will involve leaving the shutter open for several hours. Most S/DSLRs have a setting where you can leave the shutter open for as long as the shutter button is depressed. This is denoted as “B” for “bulb” and can often be found with “T” (“time”) on older cameras where the shutter is pressed once to open and again to close.
Some basic guidelines about shutter speed are:

  • Use a slow shutter speed when: it is dull (low light levels); you are using a slow film; you are using a small aperture.
  • Use a fast shutter speed when: it is bright; you are using a fast film; you are using a large aperture.

F – Numbers

The F-numbers (Referred to as F stop) give a measure of the size of the aperture. The aperture is the opening in the lens that lets light hit the film. The numbers on your SLR relating to the size of the aperture are called ‘f-numbers’. A high f-number relates to a small aperture; a small f-number relates to a large aperture (see diagram below).


Obviously, a small aperture (e.g. f22) lets less light through the lens than a large aperture (e.g. f4) does. Therefore in very bright conditions it is often necessary to use a smaller aperture whereas in dull conditions you will need to use a larger aperture. The F numbers are found around the rotatable ring on the lens, usually behind the focusing ring on manual SLR cameras. Note that this is part of the lens itself, rather than the camera. Different lenses will have different ranges of apeture.

Depth of Field

The aperture also affects one other very important variable known as “depth of field”. Take a newspaper or magazine and have a look at the photographs in it. You should be able to notice that in some, only a small part of the photograph is in focus (e.g. a person) and everything in the foreground and background is out of focus and blurred. In others you may find that everything in the photograph is in focus. This difference arises from using different apertures.
A shallow depth of field is produced by using a large aperture (f5.6 or lower) as in this picture:

DOF - Shallow

A deep depth of field is produced by using small aperture (f8 of higher) as in this picture:

Deep DOF

ISO Number (Film Speed)

All film has an ISO (International Standards Organisation) rating. The number (you will be familiar with 100, 200 and 400) refers to the amount of light a film requires to produce a well-balanced negative (see the Film section for explanation). DSLRs also use this as a measurement of how sensitive the sensor will be to light, although in the digital case it is adjustable. Low ISO values means a film isn’t very sensitive to light, and a high number means it is very sensitive to light. This is also called the film speed, as a lower ISO means that longer shutter speed must be used to get the same exposure. It not a simple case of always using a really high ISO however: in DSLRs this can lead to a phenomenon called noise. This is where an image has many oddly coloured pixels, and is almost always to be avoided.

Focal Length

While not part of the camera itself, the focal length of the lens is also important. These are measured in mm, with some common ones being 28mm, 50mm, 18-55mm and 75-200mm.
The focal length relates to how zoomed in the image is: a larger focal length lets you see things that are further away. 18mm (the widest angle most cameras will have) is good for things such as landscapes, 50mm is ideal for portraits and 300mm is good for wildlife and sports photography (as you will be further away).
Lenses with only 1 focal length are called prime lenses, and are normally better quality. This is because they have wider apertures, and less glass inside making the images sharper. Combined with apeture range, these form the best way of describing a lens.

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