Of the various controls on your camera the aperture and shutter controls are the ones which are going to give a lot of control over the content of your finished photographs. It is important to understand from the outset what they are each responsible for and how they affect each other. We have already looked at how the aperture and shutter affect exposure and thier relationship in that context. As you, hopefully, know you can use many combinations of shutter and aperture yet still retain the same exposure value, so we are now going to take a look at the factors which will influence how you will select a particular combination of shutter and aperture.
In a nutshell, the shutter controls movement, which can be subject movement or camera movement (shake), and the aperture controls how much of the scence (from front to back) will be in sharp focus. This area of sharpness is known as the 'depth of field'. Depth of field is actually influenced by two factors: Aperture and focused distance.
Juggling.
Much of the use of aperture and shutter is juggling one with the other. If you want a lot of depth of field you will have to select a small aperture. To counter this you will have to select a shutter speed that will;
- give you the correct exposure.
- be sufficiently fast enough to freeze movement within the scene.
- be fast enough to prevent camera shake.
If you want to capture fast movment you will have to select a reasonably fast shutter speed. To counter this you will have to select an aperture which will;
- give you the correct exposure.
- be small enough provide sufficient depth of field.
There will be many occasions where you will have to make compromises, particularly if you are hand holding your camera. Shallow depth of field is fine so long as the most important part of the suject is sharply focused and some subject movement may also be acceptable but camera shake will consign just about anything to the bin. Unless , of course, the picture is very newsworthy or is of personal significance.
We will go on to look at the aperture shortly but first we will look at the shutter, shutter speeds and the dreaded camera shake. It happens to everyone at some point and you can't say 'I don't know whats wrong , this has never happened to me before'.