Exercise – Focus at Different Apertures.

The aim of this exercise is to show how altering the aperture will alter the depth of field in the picture, that is, how much of the picture is in sharp focus. A wide aperture gives a small depth of field so only a small part of the picture will be sharply focused while a small aperture gives a large depth of field and therefore more (or all) of the picture is in focus. This is important to consider when setting up the camera as there are times when you may want the whole picture in focus, for instance in landscapes, and other times when it gives a more interesting effect to have some out of focus areas such as the background in a portrait.

I made several attempts to show this, initially trying outside using a row of houses, a pathway lined by trees and a fence and steps. The variation of focus could be seen, however did not make a very obvious change in any of these situations. This was probably because the light was not very bright and I had to give a fairly long exposure time at f/22 and therefore the picture was not pin sharp. I was also taking distance photographs and the effect of varying the depth of field is less in this case.

Example 1.
                      f/2.5                                        f/6.3                                        f/16

I then repeated the exercise with a still life set up using a tripod with the jugs lit from the side with a spotlight. I used a pancake lens with a focal length of 20mm (equivalent to 40mm) and was close to the jugs. This shows a much more obvious effect of the changing aperture. My preference her is the 2nd picture with a slight softening of focus to the rear as the gaze concentrates on the central jug without being too distracted by the out of focus areas that occur in picture 3.

Example 2.

                                                               aperture f/16 – the whole picture is in focus
                                                 aperture f/8 – mostly in focus but the back is slightly soft
                              aperture f/1.7 – the only area completely sharp is the central jug that is at the focal point

Exercise – Focus with a Set Aperture

The aim of this project was to show the different effects obtainable using a set aperture with the lens as wide open as possible. These are caused by focusing on  a different part of the picture. Using a wide aperture allows for a reduced depth of field therefore you can have one part of the picture more sharply in focus than the rest of it. This allows the eye to be drawn initially to different parts of the frame.
In this instance I used a 14 – 45 zoom lens where the widest aperture was 3.5. A more obvious effect could have been demonstrated by using a lens with a wider maximum aperture. I tried a variety of possible scenarios including a row of baskets of crisps, a group of outdoor cafe tables and an ornamental stone wall. Both the baskets of crisps and the cafe tables showed the effect but I felt in both cases the photograph that showed the scene best was the one that had the whole area in focus rather than a limited portion of the scene.
Example 1.
In the stone wall pictures the effect is fairly subtle but definitely alters the way the eye is led into the picture.
                            
                                                                            Focus point  - start of line    
                                                                                             Focus point - mid line
I prefer the first photo where the pillar to the right of the frame is the point of focus. I find that this makes my eye settle on the photo and then I look across at where the line of pillars leads too. In picture 2 I am not sure which way to look first and find this less satisfying as a picture.

Example 2.
Two-tone versions of a close up section of the pillars.
                                                                                 Focus point in the pillar to the right.


                                                                      Focus point in middle of the frame.
In this pair of photographs I prefer the 2nd one where the focus is in the centre of the frame. This enables my eye to rest on one point and then look around the edges and it feels more balanced, however the first photo does have a tension that makes me want to look beyond the frame to complete the image.

This pair of pictures differ from the first pair in that one is looking at a specific and close point rather than into the distance. The change of viewpoint clearly effects where the focus should be placed and demonstrates that there is no ‘correct’ answer that suits all images.