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Photographic Sharpness (This article is reprinted from the Jan.-- Mar. 1995 issue of the Examiner, published by the Pacific Northwest Division of the I.A.I.)
by CRAIG COPPOCK Sharpness in photography is a double edge sword. Sharp skills and sharp equipment are needed to achieve sharp photographs. High quality lenses are the first step toward sharpness. The lens is responsible for focusing the light, correcting for distortions and flare. Use caution when choosing camera lenses. Each of the major camera manufactures have a lens line to complement their cameras. Many of the manufactures have a multi--stage lens line. By multi--stage I mean that there are low cost lenses for beginners and tyros and an advanced amateur/professional line. Low end lenses are for the limited use such as birthdays and vacations. These lenses, in general, are constructed of cheaper materials that will not stand up to everyday use. Also these lenses often do not have the light gathering capabilities as indicated by their maximum aperture. Most importantly is that top quality glass is reserved for the professional lenses. This special low dispersion glass (ED, SLD, L, etc...) improves sharpness by better controlling the light as it passes through the lens. Improved sharpness can also improve contrast. These Pro lenses will often have the larger apertures to gather more light. On a night scene the difference between an f2.8 and an f4 lens is a faster shutter speed if wanted, a longer effective flash distance, and easier focusing. These are just the most noteworthy reasons. There are several other good reasons to own the top quality lenses such as improved distortion correction, and some other optical reasons. With single lens reflex cameras you will again find quality differences that can lead to improving photographic sharpness. The advanced amateur/pro cameras will often have special mirror dampeners to reduce vibration of the rapid return mirror. These cameras will often include mirror lock up for high magnification photographs. Some models will have this feature combined with the self timer. Pro cameras often have ultra light weight shutters that, consequently, reduce vibration in efforts to achieve faster shutter speeds and flash synchronization. Tripods and monopods are other very important pieces of equipment for improving sharpness. A sturdy tripod is, of course, mandatory in a low light level scene. No matter how hard we try to hold the camera still, without a tripod there will be some camera movement recorded on the film. This is a reduction in sharpness and contrast. There is a general rule of using a shutter speed no slower than that of your lens focal length when hand holding your camera (such as a shutter no slower than 1/125 when using a 100--135mm lens, or a shutter no slower than 1/500 when using a 500mm telephoto lens). Yet, it is very important to understand that this guide/rule is for snap shot's of Jr.'s birthday party and not for a crime scene. For a very long telephoto lens a tripod is a necessity , along with a cable release. For 600mm and up, a ballast hung under the tripod will help absorb camera vibrations, movements and a light breeze. Monopods are a great help for reducing camera movements during day time photography without seriously slowing a photographer down. Some tripod manufactures make quality tripods that convert to a monopod by removing the center column. Quick release tripod leg adjusters and a quick release camera plate are important features to look for when buying a tripod. A tripod that is easy to use will get used more often. Sharpness really counts when your photographs are enlarged to 20 x 30 inches and 12 people, whom you have never met, are judging your competence by the quality of your photography. KEEP SHARP.
This article was reprinted in “THE PRINT” |