In the next part of the Know Your Camera assignment we have looked at depth of field.
Depth of field is the term used to describe how big or small the focus point is in a photograph. A wide or deep depth of field is where all or most of the photograph is in focus and a shallow or narrow depth of field is where a small portion either side of the focal point is in focus.
Landscape photographs often use a wide depth of field in order to keep all the detail in the photograph sharp. When you want to focus in on a detail in an image and keep the surrounding area blurred a shallow depth of field is more appropriate.
Generally a shallow depth of field is achieved by using a wider aperture and being closer to the subject. Therefore a wider depth of field is achieved by using a smaller aperture and being further away from the subject.
You may also need to change the ISO in order to reduce shutter speed times.
I took these two photographs of coloured glasses. The first photo was taken at 20s at f29 in order to ensure that, even though I focussed on the dark blue glass, all of the other glasses are also in focus.
The second photo was taken at o.6s at F5 in order to make the blue glass the only glass that is totally in focus.
Clearly, at these shutter speeds I needed to use a tripod to steady the camera. I could have achieved an even wider depth of field if I had been able to move further away from the glasses.