Friday, 1 October 2010

A way of seeing: Project - Focus

Exercise: Focus at different apertures:

The aim of this exercise is to explore the relationship between aperture and focus, or depth of field.

Plan:  The previous exercise was indoors with vodka minatures.  As I would be stopping the lens down in this exercise I decided that outside would be best otherwise I would need quite long exposures or a flash.  Using flash would set a continuous speed and therefore would not demonstrate the relationship between speed and aperture.

Results and reality:  My first set of images were of some railings on a bridge but the difference in the images was not that great; visible on inspection but not obvious when small and posted on a blog.  I don't have a fast lens (yet) so the best way to create the desired effect was to use the zoom from a distance with a max aperture of F6.3.  I then went into the garden and put some pegs on the washing line at regular intervals and kept them the same colour to avoid distraction.

 F6.3 1/125sec

F14 1/25sec

F40 1/3sec

The red lines show the areas in each picture that have remained in focus, increasing as the aperture gets smaller.

Learning points:

Think how the images are to be used - my initial set were fine when viewed full size on a 24" monitor but not great on a blog.

With a combination of focal length and aperture you can isolate or accentuate any part of an image to attract the viewer's eye.  Importantly you are actually isolating a plain.  Looking at the results, the red lines show areas at the bottom right that are in focus so I have not just isolated the pegs but also areas of the washing line that are on the same plain, which was not the desired result.

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