Photographers commonly refer to the lens as the eye of the camera. So, if you could imagine yourself as the camera what sort of lens would your eye be? In other words, which camera lens is the closest equivalent to the human eye in terms of field of view, focal length and aperture? By measuring the physical refraction in the eye, scientists have concluded that the focal length of the human eye is between 22mm and 24mm. When dilated, the pupil has a diameter of 8mm. Using these two measurements, studies have measured the f-stop of the eye to be f/3.2 to f/3.5.
Now, before you rush out to buy a 24mm f/3.5 wide-angle lens, thinking that this will be closest to your own vision, consider this: the measured focal length of the eye isn’t what determines the angle of view of human vision! This is because only part of the retina processes the main image we see, known as the ‘cone of visual attention’. The area outside of the cone is what we call our peripheral vision. Studies measuring the cone of visual attention – what photographers equate to a lens’s angle of view – have found it to be 55 degrees wide. On a 35mm format/full frame sensor, 55 degrees angle of view is provided by a 43mm lens. However, the total angle of view of the human eye (including the peripheral area in which we can see movement) is 160 degrees, yet outside of the cone of visual attention we can only recognise broad shapes and movement, but no detail.
TOTAL FIELD OF VIEW
Simply, the wider focal lengths shorter than the 50mm ‘standard’ lens (the common starting point for many photographers), provide a field of view similar to most of our own visionary experiences. Of course, our eyes cannot zoom, which is why many choose a telephoto lens or zoom as their next major purchase. The excitement of seeing a subject ‘up close’ with expression and detail not visible with the naked eye, makes a telephoto lens a hugely attractive choice, but lens focal lengths of 400mm, 500mm and 600mm are notoriously bulky and not easy to handle or transport.
For years these lenses have been de rigueur for sports and wildlife photographers, but it is the wide-angle focal lengths that match our ‘total field of view’ (and therefore the ‘cone of visual attention’ as well), that are gaining popularity with photographers, cameramen, and viewers in recent times.
Last year, the winning image of the prestigious Wildlife Photographer of the Year competition was a wide-angle photo taken remotely using a camera positioned in a tree 30 metres above the ground. In the past, the vast majority of winning images have been made with the photographer behind the camera, usually fitted with a telephoto lens. This time the photographer, Tim Laman, devised a set-up for a wide view looking down on a male orang-utan climbing a tree to reach the fruit high in the rainforest canopy.
For Laman, the backdrop of the rich Bornean rainforest was an important element to his composition, providing the context of the orang-utan in his environment. The photographer himself could not be in the desired position – his presence would have completely deterred the orang-utan – so Laman spent three days climbing up and down by rope to position several cameras which he could trigger remotely. This set-up gave him the chance to not only record a wide-angle view of the forest below, but also a view of the orang-utan’s face from above.
It was a shot that Laman had long visualised and, importantly, the greater depth of field provided by the wider view of the camera lens ensured the whole composition from the orang-utan’s face to the jungle below was sharply rendered.
Depth of field is an important consideration in photography: it is the area in front of and behind the point of focus that is also in acceptable focus, and the shorter the lens focal length, the greater the depth of field available.
Remote camera set-ups such as this are always fitted with shorter focal length lenses because the combination of a wide view and great depth of field ensures an image of enormous detail and sharpness.
Of course, keeping everything within the frame in focus from the minimum focusing distance to infinity has long been the objective of the landscape photographer, and a wide-angle lens is the first choice for those wanting to capture the wide sweep of an impressive view with everything sharply rendered. While it is not surprising that the immediate response of many people to seeing a spectacular view for the first time is to take a picture that is ‘exactly as I saw it’, the resulting image often fails to match the expectation. This isn’t because the wrong focal length – say a 24mm wide-angle – has been chosen, but simply because the lens has captured more than our ‘cone of visual attention’ and thereby included elements and details or distracting areas that diminish the image as an aesthetically pleasing photograph.
The solution is to spend more time evaluating the scene through the camera viewfinder before taking a picture. For this reason, a tripod is a vital addition to the camera for landscapes, providing the support and stability to compose the view precisely and allow the photographer to check every part of the frame. This is, after all, the view as seen by the lens, not what was first perceived by the human eye.
Landscape images with a wide-angle lens require a breadth of attention to the scene beyond what is initially noticed by the photographer. After all, there is more to what is framed than the wide expanse; there is also great height from the sky above to the foreground at our feet, as well as an infinite depth to the horizon in the distance. Indeed, the main focal point within our ‘cone of visual attention’ occupies the central portion of the frame, which is only a part of the total scene as framed by the lens. For this reason, photographers working with wide-angles typically look for a foreground detail or object in the lower half of the frame to lead the viewer’s eye to the main centrally-placed subject, providing compositional balance to the overall scene.
Mounting the camera on a tripod makes it easier to carry out the precise and incremental adjustments required for a more considered composition. Another advantage of the tripod is that it allows for more careful selection of the focus point, particularly for those important foreground elements that are close to the lens. Choosing a foreground subject becomes essential the wider your angle of view. Ultra wide-angle lenses of 20mm focal length or less bring more of the foreground into the overall field of view, resulting in a closer subject-to-camera distance for any subject that occupies this part of the image, such as a rock, lake or river edge, or gate post.
However, focusing on the closest part of the scene, even with the greater depth of field offered by a wide-angle, may result in a softening of the distant parts of the view. By focusing just beyond the foreground subject, say a third of the way into the scene, the depth of field produced by smaller aperture settings will ensure there is ‘front-to-back’ sharpness.
Of course, for many distant landscape subjects, infinity focus will apply and the wide-angle lens will almost guarantee front-to-back sharpness across the whole frame. After all, stopping down the aperture increases the amount of depth of field and a tripod will also keep the camera still and free of movement and vibrations during long exposures.
BENEATH THE SURFACE
The wide view is also the favoured perspective of underwater photographers who frequently shoot with ultra wide-angle focal lengths, including the shortest lens of all, the aptly named ‘fisheye’. These lenses typically deliver 180-degree angles of view or more, with maximum depth of field and infinity focusing.
While the principles for attaining good photographs underwater are the same as for the land-based photographer, there is one very significant difference: water is 800 times denser than air, so light starts scattering immediately it passes beneath the surface. At a depth of two metres infrared light reaches its limit; ultraviolet light cannot penetrate deeper than six metres and at 35 metres all light is absorbed. Consequently, the use of an underwater flash (or strobe) is essential in restoring the natural colours of fish, coral and other sea life at these depths.
Also, the refraction of light through water makes marine subjects appear a third larger than they really are. When taking refraction and the loss of light and colour beneath the surface into account, then the wide view really is the only lens choice. It also means there is no alternative to getting extremely close to the subject for frame-filling images of large sea creatures such as seals, dolphins, whales and sharks.
Wide-angle Lens Photography by Joseph Paduano; Amherst Media; £12.99 (softback)
Digital Landscape Photography by Michael Frye; Ilex Press; £14.99 (softback)
Landscape Photographer of the Year: Collection 10 by Charlie Waite; AA Publishing; £25 (hardback)
Lens option: Wide-angle zoom
Looking for more than one wide-angle focal length to cover your total field of view? Then it is hard to go past the SIGMA 24-35mm f/2 DG HSM Art Zoom (£950) which covers the traditional wide-angle focal lengths of 24mm, 28mm and 35mm with a constant f/2 maximum aperture. Also impressive is the minimum focusing distance of 28cm and a built-in hypersonic motor (HSM) for near-silent AF operation.