Multiples: what they are about

The images in the “Multiples” gallery are an ongoing project exploring the relationship between viewing distance and perspective distance.

Put simply, the viewing distance is the distance from which one would normally choose to view an image. The perspective distance is the distance from the image at which distortions due to the focal length of the lens are cancelled out (if you look at a wide-angle image from very close, the edges stop looking stretched because you are looking at them obliquely).

At a ‘standard’ focal length (approx 60mm on full-frame 35mm format), the viewing distance equals the perspective distance, and the central group of four images were each shot at this focal length. Stand far enough away to view each of these comfortably, and there will be no distortion.

The image on the left of the triplet is shot at half this focal length, but if you do not move further away then you are still at the perspective distance for this lens/image size combination and there will be apparently no distortion as you look at he image as a whole.

The 16 images on the right are all shot at aprrox 120mm focal length equivalent. If you do not get closer then your are at the perspective distance for this lens/image size combination and there will be no apparent distortion as you look at each component in the matrix.

What is just about discernable, is how the spatial arrangement of elements in each of the images changes between focal lengths. This is to be expected… a wide angle lens works by cramming more of the image towards the centre of the shot thus stretching out the things that are at the edges, but we almost never get a chance to examine this effect measureably. As it turns out, in normal circumstances it is quite mild at these focal lengths. But it is there… and one of the reasons a panorama stitched from several standard lens images will look very different from one shot using a single image made with a wide angled lens.

Since the effect is often barely noticeable, you might ask why I don’t just shoot all three blocks at 30mm focal length equivalent and then cut them up to the right size. It is a question I have often asked myself as I struggle to align all 16 of the 120mm images correctly during shooting (and again when I have to throw away an entire matrix because one of the elements is misaligned). But that would be too easy, and in some cases (Bordeaux fountain, for instance) the effect is very pronounced. Having to re-frame each individual component during shooting certainly concentrates the mind on the multitude of different compositions that there are in each matrix, makes one question how we actually look at a scene laid out in front of us, reveals just how unlike reality most images are, allows time to weave its magic through the piece… and generally prolongs the flow state.

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