The Camera Essay Research Paper The most — страница 4

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lengths do the same. For the maximum depth of field, that is everything seems to be in focus, a low aperture on a lens with a generally lower focal length at a great distance will be the best for producing this. Sometimes, a photographer will get what is known as a lens flare. What that is a reflection on the lens from unwanted light. Lens companies combat this with a special coating that absorbs light rather that reflecting it. This is similar to the coating on the stealth fighter. Lens coatings also increase contrast. Another way to prevent this unwanted light is with a lens hood. This simply blocks the light from the sides to prevent the light rays from striking the glass at its critical angle causing flare. Light metering is an essential advancement in photographic

technology. Developed in the 1930 s, light meters were hand held and could be very bulky. They later incorporated them into the cameras in the 1960 s. This advancement helped photographers frame the shot and correct the exposure in the same step. There are four kinds of internal meters. Match needle, aperture priority, shutter priority and digital readout. Match needle systems require you to match two needles to correctly expose the film. The aperture priority automatic system eliminates one variable, the aperture. It automatically adjusts the aperture setting and all you have to do is set the correct shutter speed. The shutter priority automatic system allows the camera to take control of the shutter speed while you adjust the shot to the correct aperture. The digital readout is

on most fully automated point and shoot SLRs, it adjusts everything for you or allows you to see the correct settings for both aperture and shutter speed and manually adjust them both. All metering systems share one thing, they respond to the world as if they were one uniform shade of gray. The shade of gray is 18% gray, named for its reflection ratio. It represents the average amount of light reflected by an average outdoor object. This is a reflected light meter. The other type of meter is an incident light meter. It measures the amount of light falling on the scene. Most meters are averaging meters because they average all the light in the shot. Meters that measure the amount of light in a narrow angle are called spot meters. Though Averaging meters are somewhat less accurate,

spot meters are often very hard to use and you must be able to interpret their readings. With recent advances in light metering and electronics getting smaller and smaller by the day, cameras are now being equipped with automatic systems such as autofocus and autoaperture. Autofocus is based on the principal of reflection. There are two autofocusing systems, active and passive. Active systems use reflected infrared light or ultrasonic sound to judge the distance between the object and the camera. This is usually accurate, but not always. If there is an object in front of the one you are trying to focus in on, it will focus in on that abject and blur the rest of the scene. Passive systems correct the problems with active systems, but come with their own. Passive systems use

special sensors behind the lens to correctly adjust the camera to the maximum contrast in a rectangular target. If you are photographing a large sail on a ship, for instance, the autofocus will not work. Wit advancements in internal light metering systems, cameras have a system for measuring the amount of light on the scene and can adjust automatically the correct aperture using a microprocessor. The same system can be used to adjust the shutter speed too. Some cameras have both systems. The absence of adequate daylight in any scenario calls for the use of artificial lighting. The most common sources of artificial light are tungsten lamps, quartz lamps, and the most widely used and most useful, the electronic flash. The electronic flash was invented by Harold Eugene Edgarton. He

developed the electric strobe light that you would see at any club or concert, or stroboscope. With this invention, he photographed a bullet in mid flight at a flash rate of 1/500,000 of a second. Today s electronic flashes fire at a rate of 1/1000 of a second to 1/5000 of a second. Though, rates of 1/100,000 of a second are now more readily available. Flashes vary in size, from small battery operated ones that sit on top of the camera, to very large expensive studio flashes that are required to be plugged in. The small units are sufficient enough to flood an already lit scene to get rid of harsh shadows, light close ups and portraits and other such snap shots. Studio flashes are much brighter and can flood the scene with immense amount of light. Their flash rate can be varied