Does zooming in from a fixed viewpoint change the appearance of things? If you enlarge and compare individual elements within the first and last shots of the last exercise you can see that their ‘perspective geometry’ is exactly the same. To change the way things actually look, a change in focal length needs to be combined with a change in viewpoint.
Select your longest focal length and compose a portrait shot fairly tightly within the frame in front of a background with depth. Take one photograph. Then walk towards your subject while zooming out to your shortest focal length. Take care to frame the subject in precisely the same way in the viewfinder and take a second shot. Compare the two images and make notes in your learning log.
As you page between the two shots it can be shocking to see completely new elements crash into the background of the second shot while the subject appears to remain the same. This exercise clearly shows how focal length combined with viewpoint affects perspective distortion. Perspective distortion is actually a normal effect of viewing an object, for example where parallel train tracks appear to meet at the horizon. A ‘standard lens’ – traditionally a 50mm fixed focal length lens for a full-frame camera (about 33mm in a cropped-frame camera) – approximates the perspective distortion of human vision (not the angle of view, which is much wider). A standard lens is therefore the lens of choice for ‘straight’ photography, which aims to make an accurate record of the visual world.
My shots
Once I’d convinced my wife to take part, and the weather had finally turned into something that resembled spring, I took my camera and tripod into the garden and set up at the bottom of the drive. I positioned my subject at the other end of the drive in a suitable spot for the camera’s maximum focal length.
The first shot(with a grumpy subject) was cropped quite close by the lens and gave a fairly shallow depth of field.
The second shot, with the shortest focal length captured much more of the surroundings with a more ‘wide-angled’ view. It gives more of a sense of depth than the first shot as it is closer to the ‘standard lens’ length and therefore gives a truer view. Below are the highlighted areas of the photograph that can be seen with a shorter focal length.
Reflection
I hadn’t previously looked too closely at what effect the zoom had on a subject, its surroundings and the perception of the subject matter. This exercise has highlighted what a longer lens can do and what advantages and disadvantages it has. The focal length of my 70-300mm lens definitely exaggerated this.
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