Designing with the aperture

I have already explained that the aperture setting is an important setting for correctly exposing an image in the article Basics – Exposure. However, it would be boring if you could only use the aperture to make a picture brighter or darker; it is much more interesting to use it for composition.

Depth of field

In most cases, what makes a beautiful photo is the fact that some point in the picture is in focus. Sometimes this should be a face, sometimes a whole landscape.

The problem with photography is that people and landscapes have depth (I’m not so sure about some people). The environment we photograph is three-dimensional, but our photo is very flat, i.e. two-dimensional.

Without going too deeply into optics, this means that we can only ever focus on one plane in our image, namely the one we are focusing on, everything that is even a little bit in front of or behind it is “out of focus”.

Fortunately, the human eye is not so good that it immediately recognizes small deviations and just because a point cannot be sharp in purely mathematical terms, we also feel that way when we look at it.

(l) Shutter open, (r) Shutter closed

The further you close the aperture (larger f-numbers), the greater the depth of field. As already mentioned, this is due to the fact that a point is only sharp if it is also depicted as a point on the sensor.

The lens focuses each pixel and images it as a peak on the sensor. However, if the pixel is further away or closer, the peak is often in front of or behind the sensor plane; instead of a dot, a disk is then imaged and we perceive this as blurring.

If you now reduce the aperture and no longer let in the ‘thick’ beam of light, the cone of light that hits the sensor becomes sharper. The blur circle shrinks. The area that we perceive as sharp becomes larger.

Controlling the depth of field has a big influence on how an image looks. The two photos with my wonderful model were taken once with the aperture open and once with the aperture closed . You can see how the aperture affects the background.

An open aperture is always very useful when I want to draw attention to the object in focus. The best example is all kinds of portraits. If the aperture is open, the background becomes blurred and the person stands out more clearly.

It’s different when the context of the surroundings is important to me. If I want to show where the person is, i.e. if I want to add more information about the situation, then I better close the aperture a little so that you can still see something of the surrounding situation.

Between completely open and completely closed, there are lots of gradations that leave plenty of creative scope.