Rodney Campbell's Blog

There are usually many different combinations to achieving a ‘correct’ exposure but whilst the image may be ‘technically correct’ only one of these combinations may result in the image you have in your minds eye when you take the photograph.

In an earlier blog post I discussed the three factors which when combined set the exposure (Aperture, Shutter Speed and ISO) and depending on what combination of values is chosen the resultant image can be vastly different in feel, impact and meaning.

One of the most expressive tools you have at your disposal to control the look and feel of your photograph is by adjusting the Aperture.

The following sequence of images are aimed at giving you a feel for how the same image may change as you adjust the aperture used to take the same photo. Adjusting the aperture for a shot most directly affects the depth of field (the amount of the photo (in front of and behind the selected focus distance) which appears to be in focus).

The sequence was taken within seconds of each other with both the subject and the camera staying in the same locations – also for each shot I was attempting to focus on the subjects eyes. I should have used a tripod for this since even 1/60s handheld for a 135mm focal length isn’t ideal so not all of the shots are sharp.

All shots used the same 90mm (135mm effective) lens and I had the camera set on Aperture Priority Mode so that I could adjust my chosen aperture manually and the camera would then choose an appropriate Shutter Speed (and ISO) to match. The reason that the camera chose to adjust the ISO was because there wasn’t enough available light late in the afternoon with very small apertures to have a shutter speed fast enough (1/60s or above) when hand holding the camera.

The sequence of shots is from f/32 (smallest aperture) to f/2.8 (widest aperture) in one whole stop increments.

This first shot is taken at an aperture of f/32 which generally will give a very deep depth of field.

1/60 sec at f/32, ISO 3200, 135mm equiv

1/60 sec at f/22, ISO 1400, 135mm equiv

1/60 sec at f/16, ISO 800, 135mm equiv

1/60 sec at f/11, ISO 400, 135mm equiv

1/60 sec at f/8, ISO 200, 135mm equiv

1/125 sec at f/5.6, ISO 200, 135mm equiv

1/320 sec at f/4, ISO 200, 135mm equiv

Finally with the lens wide open at f/2.8 the depth of field is so shallow that even the tree branch just behind the subjects head is completely blurred and without detail and the subject pops off the image.

1/500 sec at f/2.8, ISO 200, 135mm equiv

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