Fisheyes and Wide Angle-Lenses–What You Need to Know
What is a wide angle lense? Wide-angle lenses are basically any lens with a field of view wider than a standard lens. On a 35mm film camera or full-frame digital, this is any lens with a focal length of 35mm or shorter. Wide-angle lenses are great when you need to take in a lot of a scene. This could be a dramatic shot of a landscape or a picture showing the interior of a room. Wide-angle lenses vary wildly in price, with the focal length the primary factor in determining cost. Focal lengths close to normal—28mm to 35mm for full frame—tend to be affordable simply because such lenses are easy to produce. But the wider you go, the more the light has to be bent and the more complex the optics have to be. Below are examples of various wide-angle lenses and the best shooting situations in which to use them.
Extreme Wide Angles
Extreme wide angles—wider than 24mm or so for full-frame—can take in more than can be seen by a single glance of the human eye. A shot taken with an extremely wide-angle lens can also have something of an immersive quality. Since much of a scene can be within the depth of field, objects across the whole scene can appear very sharp. As described later in section 5.9, portraiture with these lenses can take on a strange bulging and grotesque appearance.
These visual qualities are exploited by filmmakers such as Terry Gilliam, who is well known for his use of wide-angle rectilinear lenses (not fisheyes). People sometimes refer to 14mm cinematic lenses as “Gilliams” for this reason, though note that the image area of 35mm movie film is actually about the size of an APS-C subframe DSLR, and not the size of a full-frame 35mm still camera. Although they can yield striking photographs, wide-angle lenses can also be difficult to use well. Since they take in so much of a scene, photos can appear cluttered or busy or lack a main point of interest. Extreme wide angles tend to be very costly and often suffer from very soft or even blurry image corners. SLR wide angles must have retrofocus optics, which is a significant reason for the expense.
Fisheye lenses are a very specific form of wide-angle lens. Unlike rectilinears, fisheyes don’t try to keep straight lines straight. Instead, they demonstrate extreme uncorrected barrel distortion. Lines that happen to pass through the very center of the image will record as straight. All other lines will appear to bulge outward. There are two basic advantages to fisheyes. First, they can take in massive amounts of a scene, and second, the curving look can yield interesting visual effects. The primary drawback is related to the second point—not everybody likes or appreciates the classic fisheye look. The lenses can also be difficult to use, both aesthetically and practically. For example, it’s all too easy to get your feet, your shadow, or tripod legs showing up in a fisheye shot.
Full Frame Fisheyes | There are two basic types of fisheye lens, categorized by focal length. Fullframe fisheyes take in a full 180 degrees of the scene when measured diagonally across the frame. They’re basically as wide as you can possibly get without getting dark areas in the corner of the picture. These lenses have focal lengths of 15 or This shot of London’s Natural History Museum was taken with a full-frame fisheye. It reveals the ground floor beneath the pedestrian bridge, for a rather M. C. Escher–like view. 10mm fisheye, 1.5x subframe camera. f/16, 5 sec. ISO 200. 16mm when designed for full-frame 35mm cameras and around 10mm for subframe cameras. 15mm and 16mm full-frame fisheyes, when used in cropped cameras, just act as moderately wide-angle lenses, with only a little fishiness visible. Note the potential for confusion here, as “full frame” refers to the ability of the lens to cover an entire image frame of whatever camera is being used, not whether the sensor is the size of 35mm film or not.
Circular Fisheyes | Circular fisheyes are the most extreme wide-angle lenses available. Most take in an amazing 180 degrees of the scene when measured across the short dimension of the image frame. This means that, when pointed up vertically, they can take in the entire sky.
Defishing | Since the fishy quality of a lens follows straightforward optical geometry, it’s actually pretty easy to use a computer program to correct for fisheye barrel distortion. This lets you use an inexpensive fisheye lens as a sort of poor person’s rectilinear wide-angle lens. The process results in heavy loss in quality in the corners because you’re stretching the image most in the areas where the lens has its worst quality. Therefore, a lot of cropping is needed, and so the defished image will have a decreased field of view.
This post was taken from The Lens by NK Guy