Focal lengths

Having tried the test of looking at a scene with the naked eye, estimating the angle of view and then looking at the scene through the camera viewfinder and a standard lens I now better appreciate the behaviour of the camera optics and the relationship in optical performance terms to the human eye.  With the naked eye(s) I estimate my angle of view is in the region of 180 degrees; but this does raise the question of what actually constitutes the “angle of view”.  By design we have quite an extensive angle of view, or peripheral vision, but at the extremities the objects are not clear/sharp and it is generally accepted that the peripheral view is more about detecting movement; contrast with the view through the viewfinder where there are hard boundaries.  I did find that the view through the camera closely represents that part of the scene I observed with the naked eye to be sharp.  This, therefore, confirms the correlation between the angle of view of the standard lens on the camera and that of the human eye(s) in terms of a sharply focussed image.

For the exercise I selected a beach/lighthouse scene as I thought it would best illustrate the differences focal length makes to the angle of view, there being little background clutter but with some definition.  The camera was tripod mounted.

The series of shots above clearly illustrates the difference in angle of view as the focal length is changed; wide angle of view with short focal length to small angle of view with long focal length.  For me the large angle of view gives a feeling of the expanse of the area with the lighthouse intruding into it, albeit with a real role to play.  As the angle of view reduces it becomes more about the detail of the lighthouse and, finally, at the smallest angle of view, the lighthouse dominates the scene.  I chose not to change the composition as I felt that the required effect had been illustrated using the lighthouse as the main component but the detail of the town in the distance at a narrow angle of view also serves to illustrate the utility of the telephoto lens in landscape scenes; for some time I was wedded to the idea that landscape equals wide angle lens.  Clearly, though, the rule of thirds did not get much of a look in here!

Reference List:

Freeman, Michael, (2007).  The Photographers Eye:  Comosition and Design for Better Digital Photos, The Ilex Press


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