Exercise three: Focus at different apertures

The brief for this exercise was to choose a scene similar to the previous exercise (a row of things seen from angle) and take three images - one with the camera's widest aperture, another with a mid-point aperture and one with the narrowest.

To ensure that each image was framed identically I used a tripod. This was also necessary because the shots were taken in low light conditions and as such required longer exposures.

In order to get sufficiently close to the image I used a 12mm macro extension ring on my fixed 50mm Sony lens. This further narrowed the depth of field.

Widest aperture - 50mm, 1/6 sec at f/1.8, ISO 100

The depth of field in the first shot is extremely narrow, leaving only the 'X' key in focus. In fact, it's extremely difficult to make out any of the surrounding keys.

Mid-point aperture - 50mm, 3.2 secs at f/8, ISO 100

Having narrowed the aperture to f/8 the area in focus does indeed increase, but not significantly - parts of the 'Z', 'D', 'C' and 'cmd' keys are now in focus.

Narrowest aperture - 50mm, 25 secs at f/22, ISO 100

Although the depth of field is much wider not all keys are in focus, but they are all distinguishable. Those keys now in focus range from 'Z' right through to 'B'.

It was really interesting to see the effect that the macro extension ring had on the depth of field (narrowing it even further) resulting in a great effect on image 1.

The long exposure needed for images 2 and 3 meant that I used a remote trigger to fire the shots to avoid camera shake, although I did find using the camera's timer function worked equally well.

One camera option that I wasn't familiar with was BULB, which this exercise prompted me to research. I now know how to use this feature if a scene requires an exposure longer than 30 seconds.