In this exercise, aimed at helping us to understand the effects of aperture on the image, the aperture remains fixed but the focus point changes.

I used a 100mm lens at f2. This is a lovely portrait lens because of how well it isolates the subject with a narrow depth of field and how good the out of focus parts of the image look. You can read an awful lot about these out of focus areas, or bokeh, and the ways in which various lenses recreate it. In my experience, it is more about the subject than the equipment.

The depth of field on this lens is so shallow that in the first picture, we can tell that someone is holding an apple, but would be guessing to identify who – my guess is the Mona Lisa…

…I was wrong! The second picture has the same depth of field but with a different focus point. The apple held at arms length is enough to give this huge amount of blurring to areas other than those focussed upon.

This exercise teaches us that a part of the image can be isolated using the aperture to bring attention to that aspect. The eye is drawn to the objects or areas that are in focus, maybe because it has less work to do to understand what is hidden in the bokeh. If I was selling apples, the first picture may be the one I’d choose. As it’s my wife in the picture however, I much prefer the second one of course.

If I had been taking this picture for something other than the exercise, I’d choose an aperture a little smaller, but leave the focus on the apple, reducing the blur on Gosia’s face to a level that still identifies it as her but not as extreme as the first picture.