APERTURE/EXPOSURE/DEPTH OF FIELD/SHUTTER SPEED/ISO

This week we worked in the studio looking at F stops, depth of field and shutter speed which all have an effect of exposure.

Depth of Field/F stops

When a lens is focused on a point a certain distance away, there is an area in front of and behind the subject which is in focus, this is called the 'depth of field'. This area can be controlled by varying the aperture size, this controls the amount of light entering the lens. When the aperture if fully open, (f3.5) the depth of field is shallow, however this can be extended in increments up to a maximum of f22, (infinity). the larger the f number the smaller the aperture and the greater the depth of field.

Here a shallower depth of field has been used as an experiment, the boat rails and canopy are in focus but the distant harbour is out of focus.

Again a shallow depth of field with the crew man nearest in focus.

A longer depth of field brings the distant view into focus whilst blurring the foreground.

Shutter Speed

Several factors affect the amount of light entering the camera, the diameter of the aperture and the duration of exposure, or shutter speed.
Shutter speed too slow, the image is underexposed.

The main factors to be considered when deciding shutter speed are camera movement and subject movement. Shutter speeds vary from 1/1 to 1/4000. If the camera is hand held a faster shutter speed is preferable since this will minimize camera shake and therefore blurring of the image, a faster speed is also preferred if freezing of subject movement is needed. However, when photographing moving water or taking action shots an amount of blurring may be needed therefore slower shutter speeds can be used . There is a point, at slower speeds where a tripod may be needed to prevent camera shake.

Shutter speed here was too slow to capture the moving child.

Aperture size and shutter speeds are therefore linked, consideration needs to be given to the amount of light available, the distance of the shot from the camera and how much of the subject needs to be in focus.

ISO

ISO can also be used to gather more light into the lens, ISO refered to film speed when using film in a manual camera, the higher the ISO the more sensitive the film to light but unfortunately this can lead to a grainy image. ISO settings on my camera range from 100 to 3200 I have experimented with higher ISO in fading light and at night and achieved some interesting pictures as opposed to using flash.

I used a higher iso setting for this shot since it was grey and overcast outdoors therefore low light levels inside and I did not want to use flash, however the image is very grainy.

In this shot I had an incorrect setting on white balance as well as a high iso which has given a blue cast and very grainy.

I was experimenting with a high iso and slow shutter speed for these shots at halloween, I also changed the white balance to tungsten.