Using Aperture to Create Stunning Effects

The word photography literally means "painting with light." Light is a vital component of the photography process. However, if there is too much light, a photograph can be severely overexposed or "washed" out. Not enough light results in an underexposed or indiscernible photograph. Therefore, the right amount of light is necessary to get the perfect photograph.

The main function of the camera is to properly expose the sensor or film by admitting the right amount of light through the APERTURE or variable opening of a lens. Before the sensor or film is exposed, the camera measures the light reflecting off the subject. It then determines the correct aperture (f-stop) and shutter speed. (The shutter speed is the length of time reflected light is allowed to impact the photographic sensor or film. It is expressed in seconds.)

The combination of f-stop and shutter speed is referred to as EXPOSURE. The camera's exposure calculation is usually acceptable under normal lighting conditions. However there are times when the camera is fooled by tricky lighting conditions. Under these circumstances, the camera needs your help to get the correct exposure. Understanding the effects of varying aperture settings (f-stops) and varying shutter speeds, will go a long way in getting the correct exposure.

What's f2.8, f4, f8, f11 and f16?
The different f-stops of a lens is expressed as a ratio of the focal length and the diameter of the aperture.

Let's consider a 50mm prime (fixed) lens. When the diameter of the aperture is 25mm, the f-stop is 2. We get f/2 by dividing the focal length by the diameter of the aperture, i.e. 50mm/25mm = 2. When the diameter of the aperture is about 12.5mm, the f-stop is 4. (50mm/12.5mm = 4)

Some of the f-stops you are more likely to see are:

            1.4      2.0      2.8      4      5.6      8      11      16      22

The smaller numbers represent LARGE openings in the lens and the larger numbers correspond to SMALL apertures as the following illustration shows:



           f2                      f4                      f8                      f16

Using Large Apertures for Stunning Effects
Large apertures allow great amount of light to reach the photographic sensor or film. In most daylight situations a large aperture is accompanied by a fast shutter speed, e.g. f4 and 1/1000.

A large aperture produces a narrow depth of field (area of acceptable focus). A narrow depth of field creates a blurry background. Hence, large apertures are used creatively to isolate a subject against its background. This is sometimes necessary to make the subject stand out against a distracting background.

Look at this photograph of a bird of paradise (a flower). The background is totally blurred. A large aperture (f5.6) setting on a 400mm telephoto lens was used to create this effect.

Large apertures are used for shooting portraits. This allows the person to stand out against the background. Large apertures are also used when doing macro photography.

DEPTH OF FIELD EXPLAINED
Depth of field is the area in sharp and acceptable focus that stretches from foreground to backgrouind. To illustrate, imagine a photograph of a bed of roses. Likely there are a few roses close to each other that are in sharp focus. Just in front of these sharp roses, there is an area (foreground) that is acceptably sharp. Likewise there is an area behind these sharp roses (background) that is also acceptably sharp. The depth of field is that area from foreground to background that is considered to be in focus.

To better illustrate depth of field and how different apertures affect the area of focus look at these five water bottles. The camera is focused on the center bottle and the aperture is changed from f4 to f8 and then f22. Click on each image and notice how many bottles are in sharp or acceptable focus.

Large apertures (f1.4, f2.8, f4) give shallow depth of field and make your subjects stand out against an "out-of-focus" background. Here is a perfect example.

Small apertures (f11, f16, f22) give an extended (deep) depth of field and produce scenes (e.g. beaches) in which most of the view is in focus.