Before we talk about how to change the look of your images using different settings, first we should enlighten you on what the aperture settings and f-stops mean. If you were to devise a system that was intended to be confusing, you’d have a hard time coming up with anything more confusing than photographic aperture. I’ve so often seen people glaze over within five seconds of the start of an explanation, their minds a whole galaxy away – anywhere, so long as it’s not here listening to f/stops, depth of field and so forth. But when you split it up, it’s pretty easy.
So, what is aperture?
The basic idea is that light reaches your camera’s sensor (or film) through a hole.
With pinhole cameras, it’s literally that: a hole in a light-tight box projects an image on the inside. With cameras, we put some glass around the hole to make the image sharper. But essentially, it’s still a hole. History would have been different if photographers talked about ‘hole numbers’ or adjusting the size of their ‘lens hole’ but somehow that did not sound cool – even in the 1870s.
The bigger a hole, the more can go through it. It’s the same with lens aperture: the larger the aperture, the more light gets through to the sensor. Obviously this affects the exposure of your image.
So photographic aperture is the hole in the camera lens which lets light in.
Aperture and depth of field
So much for aperture and exposure. What complicates the whole subject further is that aperture affects two quite different things independently. Just as shutter setting contributes to exposure but also influences motion blur, aperture setting contributes to exposure but also influences something else altogether.
Aperture is one of the factors controlling depth of field. In fact aperture is the single most powerful and easiest way to control depth of field.
Maximize your Depth of Field
While there may be times that you want to get a little more creative and experiment with narrow depth of fields in your Landscape Photography – the normal approach is to ensure that as much of your scene is in focus as possible. The simplest way to do this is to choose a small Aperture setting (a large number) as the smaller your aperture the greater the depth of field in your shots. Due to the smaller amount of light coming through you'll need to expose it for longer.
Do keep in mind that smaller apertures mean less light is hitting your image sensor at any point in time so they will mean you need to compensate either by increasing your ISO or lengthening your shutter speed (or both). Depth of field increases with distance. The farther you place the camera from your subject, the more depth of field you can obtain. Landscapes have great depth of field, while macro photographs tend to have very little depth of field because the subject is so close to the lens.