flash is a device used in photography that produces artificial light (usually 1/1000 to 1/200 sec) at a color temperature of about 5500 ° K to help illuminate the scene. The main purpose of the flash is to illuminate the dark scene. Other uses are capturing objects that move quickly or change the quality of light. Flash refers to the flash light itself or to the electronic flash unit to output light. Most flash units today are electronics, having evolved from disposable flashbulbs and flammable powders. Modern cameras often activate the flash unit automatically.
Flash units are usually built directly into the camera. Some cameras allow separate flash units to be installed through a standard "accessory mount" bracket (a hot shoe ). In professional studio equipment, the flash may be large, stand-alone units, or lampin studio, powered by a special battery pack or connected to mains power. They are synchronized with the camera using a flash sync cable or radio signal, or triggered by light, which means only one flash unit needs to be synchronized with the camera, and in turn triggers another unit, called slave .
Video Flash (photography)
Jenis
Lampu-kilat
The study of magnesium by Bunsen and Roscoe in 1859 showed that burning this metal produces light of the same quality as daylight. Potential applications for photography inspire Edward Sonstadt to investigate methods of making magnesium so that it burns reliably for this use. He applied for a patent in 1862 and in 1864 had started the Manchester Magnesium Company with Edward Mellor. With the help of engineer William Mather, who is also the company's director, they produced flat magnesium bands, which are said to burn more consistently and completely so as to provide better lighting than round wires. It also has the advantage of being a simpler and cheaper process than making round wires. Mather is also credited with the invention of the holder for the ribbon, which forms a lamp to burn it. Various magnesium tape holders are manufactured by other manufacturers, such as the Flashmeter Pistol, which incorporates a readable ruler that allows photographers to use the correct length of tape for the exposure they need. The packaging also implies that the magnesium tape does not need to break before it is turned on.
An alternative to the ribbon is the flash powder, a mixture of magnesium powder and potassium chlorate, introduced by German inventors Adolf Miethe and Johannes Gaedicke in 1887. Measurable quantities are inserted into a saucepan or trough and ignited by hand, producing a brief brilliant flash of light, with the smoke and noise that might be expected from such an explosive event. This can be a life-threatening activity, especially if the flash powder is moist. An electrically triggered flash lamp was invented by Joshua Lionel Cowen in 1899. His patent depicts a device for lighting a photographer's flash powder by using a dry cell battery to heat the wire fuse. Variations and alternatives are heralded over time and some find success measures, especially for amateur use. In 1905, a French photographer used a non-explosive flash produced by a special mechanical carbon arc lamp to photograph the subject in his studio, but a more portable and cheaper device won. In the 1920s, flash photography usually meant a professional photographer sprinkled powder into a T-shaped flash lighthouse, holding it aloft, then sparking briefly and (usually) slightly harmless from fireworks.
Flashbulbs
The use of flash powder in open lights is replaced by flashbulbs ; the magnesium filaments contained in the bulb are filled with oxygen gas, and electrically ignited by contact in the camera shutter. Flashbulbs were first manufactured commercially in Germany in 1929. Such bulbs could only be used once, and were too hot to handle immediately after use, but what cages should have as big as a small explosion is an important advance. The next innovation is the coating of flashbulbs with plastic films to maintain the integrity of the light bulb when the glass breaks during the flash. A blue plastic film was introduced as an option to match spectral quality from flash to bright daylighted films. Furthermore, magnesium is replaced by zirconium, which produces brighter flashes.
Flashbulbs take longer to achieve full brightness and are burned longer than electronic flashes. Slower shutter speeds (usually from 1/10 to 1/50 sec) are used on the camera to ensure proper synchronization. The camera with flash sync triggers a split second flashbulb before opening the shutter, allowing faster shutter speeds. A widely used flashbulb during the 1960s was Press 25, a 25-millimeter (1 inch) flashbulb often used by journalists in period films, usually attached to press cameras or twin-lens reflex cameras. The peak light output is about one million lumens. Other flashbulbs commonly used are M-series, M-2, M-3 etc., which have a small metal bayonet base ("miniature") that blends into a glass ball. The biggest flashbulb ever produced is the GE Mazda No. 75, which was originally developed for night air photos during World War II.
The all-glass PF1 bulb was introduced in 1954. Eliminating the two base metals, and some manufacturing steps are required to attach them to a glass bulb, cut costs substantially compared to larger M series bulbs. The design requires a fiber ring around the base to hold the contact cable on the base side of the glass. The available adapter allows the bulb to fit into a flash weapon that receives a closed bayonet ball. PF1 (along with M2) has a faster ignition time (less delay between shutter and peak output), so it can be used with X aligned under 1/30 sec - while most lights require a shutter speed of 1/15 on synch X to keep the shutter open long enough for the bulb to burn and burn. A smaller version, the AG-1 was introduced in 1958 that did not require a fiber ring. Although smaller and have reduced light output, it is less expensive to produce and quickly replaces PF1.
Flashcubes, Magicubes, dan Flipflash
In 1965 Eastman Kodak from Rochester, New York replaced the individual flashbulb technology used on the initial Instamatic camera with Flashcube developed by Sylvania Electric Products..
A flashcube is a module with four discardable flashbulbs, each mounted at 90 ° from the other in its own reflector. To use it mounted above the camera with electrical connection to the shutter and battery shutter in the camera. After each flash exposure, the motion mechanism of the film also rotates the 90 Â ° flashcube to the fresh ball. This setting allows the user to take four images in sequence before inserting a new flashcube.
The later Magicube (or X-Cube) retains the four-bulb format, and is superficially similar to the original Flashcube, but does not require any electrical power. Each bulb is mounted by a plastic pin in a cube holder that releases spring wires that are cocked in a cube. This wire strikes the primary tube at the base of the bulb, which contains the fulminate, which in turn ignites the shaved zirconium foil in the flash. Magicubes can also be fired by inserting a thin object, such as a key or a paper clip, into one of the slots at the bottom of the cube.
Flashcubes and Magicubes look similar but not interchangeable. Cameras that require a flashcube have round sockets and round holes for flashcube pins, while those requiring Magicubes have rounded shapes with protruding buttons and square socket holes for Magicube square pins. The Magicube socket looks like the letter X, which accounts for its alternate name, X-Cube.
Other common flashbulb-based devices are Flashbar and Flipflash, which provide about ten flashes from one unit. The name Flipflash comes from the fact that half the bulb is already in use, the unit is reversed and reinserted to use the rest.
Electronic Flash
The electronic flash tube was introduced by Harold Eugene Edgerton in 1931; he made some iconic photos, like one of those bullets that broke through the apple. The great photography company Kodak was initially reluctant to take the idea. Electronic flash, often called "strobe" in the US after the use of Edgerton techniques for stroboscopy, began to be widely used in the late 1950s while flashbulb was still in general use. Initial units are expensive, and often large and heavy; the power unit is separated from the flash head and powered by a large lead-acid battery carried with a shoulder strap. Toward the end of the 1960s, electronic flashgun of the same size as conventional bulb weapons became available; the price, although down, is still high. The electronic flash system eventually replaces the bulb as the price drops.
A typical electronic flash unit has an electronic circuit to charge a high capacity capacitor up to several hundred volts. When the flash is triggered by the shutter synchronization contact, the capacitor is released rapidly through a permanent flash tube, producing an instantaneous flash that lasts usually 1/1000 second, shorter than the shutter speed used, with full brightness before the shutter has started. to close, allowing easy synchronization of full flash brightness with maximum shutter opening. Synchronization is problematic with the lamp, which if ignited simultaneously with the shutter operation will not achieve full brightness before the shutter is closed.
A single electronic flash unit is often installed on camera accessory shoe or bracket; many cheap cameras equipped with electronic flash units. For more sophisticated and longer lighting, multiple synchronized flash units at different positions can be used.
The flashing ring corresponding to the camera lens can be used for shadow-free macro photography, There are several lenses with built-in flash ring.
In the photography studio, a more powerful and flexible studio flash system is used. They usually contain light modeling, incandescent light bulbs close to a flash tube; Continuous illumination of light modeling allows photographers to visualize the effects of flash. A system can consist of multiple synchronized flash for multi-source lighting.
The strength of flash devices is often shown in the form of guide numbers designed to simplify lighting arrangements. The energy released by larger studio flash units, such as monolights, is shown in watts-seconds.
The Nikon brand name for its electronic flash unit, Speedlight, is often used as a generic term for electronic flash equipment.
High-speed flash
Flash air gap is a high voltage device that releases flashes of light with a very short duration, often less than a microsecond. It's usually used by scientists or engineers to examine objects or very fast moving reactions, famous for producing bullet shots that rip light bulbs and balloons (see Harold Eugene Edgerton). An example of a process for making high-speed flash is a burst cable method.
Multi-flash
Cameras that implement multiple flash can be used to search the depth edge or create a stylish image. Such cameras have been developed by researchers at Mitsubishi Electric Research Laboratories (MERL). Successively flashing the strategically placed flash mechanism produces shadows along the depth of the scene. This information can be manipulated to suppress or enhance details or capture complicated geometric features of a scene (even hidden from the eye), to create non-photorealistic image shapes. Such images can be useful in technical or medical imaging.
Flash intensity
Unlike flashbulbs, the intensity of electronic flash can be adjusted on some units. To do this, smaller flash units typically vary the discharge time of the capacitor, whereas larger units (eg, higher power, studios) typically vary the charge of the capacitor. The color temperature may change as a result of varying the charge of the capacitor, thus making color correction necessary. Due to advancements in semiconductor technology, some studio units can now control the intensity by varying the discharge time and thereby providing a consistent color temperature.
Flash intensity is usually measured in stops or in fractions (1, 1/2, 1/4, 1/8 etc.). Some monolights display "EV Number", so photographers can know the difference in brightness between different flash units with different wattage-seconds. EV10.0 is defined as 6400 watt-second, and EV9.0 one stop lower, ie 3200 watt-second.
Flash duration
Flash duration is generally explained by two numbers expressed in fractions of seconds:
- t.1 is the length of time the light intensity above 0.1 (10%) of the peak intensity
- t.5 is the length of time the light intensity is above 0.5 (50%) of the peak intensity
For example, a single flash event may have a value of t.5 1/1200 and t.1 of 1/450. These values ​​determine the ability of flash to "freeze" moving subjects in applications such as sports photography.
In cases where the intensity is controlled by the discharge time of the capacitor, t.5 and t.1 decreases with decreasing intensity. Conversely, in cases where the intensity is controlled by the capacitor charge, t.5 and t.1 increases with decreasing intensity due to the non-linearity of the capacitor discharge curve.
LED Flash is used on phone
Current high flash LEDs are used as flash sources in camera phones, although they are not yet at the power level for the same xenon flash device (which is rarely used in mobile phones) in silent cameras. The main advantages of LED over xenon include low voltage operation, higher efficiency, and extreme miniaturization. The LED flash can also be used for lighting video recording or as an auto focus focus light in poor lighting conditions.
Focus-shutter sync
The electronic flash unit has compatibility issues with the focal-plane window. The focus window cover raises two curtains that crosses the sensor. The first one is open and the second curtain follows after the same delay with the nominal shutter speed. The typical modern focal-plane shutter requires about 1/200 s to cross the sensor, so at expiration times shorter than this only some of the sensors are revealed at one time. Electronic flash can have a duration of as short as 50 Âμs, so at a short exposure time only a portion of the affected sensor. This limits the shutter speed to about 1/200 seconds while using flash. In the past, slow-burning single-use flashlights allowed the use of focal-plane shutter at maximum speed as it produced continuous light for the time taken for the disclosure gap to cross the film gate. If this is found they can not be used on modern cameras because the light bulbs must be fired * before * the first shutter blind starts to move (M-sync); X-sync used for electronic flash usually only lights up when the first shutter curtain reaches the end of its journey.
The high-end flash unit overcomes this problem by offering a mode, usually called FP sync or HSS (High Speed ​​Sync), which activates the flash tube several times during the time slot across the sensor. Such units require communication with the camera and are thus dedicated to certain cameras. Some flashes produce a significant decrease in the number of guides, because each is only a part of the total flash power, but it's all that illuminates a certain part of the sensor. In general, if s is the shutter speed, and t is the shutter traverse time, the number of guides is reduced by ? s / t . For example, if the guide number is 100, and the shutter time is 5 ms (1/200s shutter speed), and the shutter speed is set to 1/2000 s (0.5 ms), the guide number is reduced by the factor ? 0.5/5 , or about 3.16, so the guide number generated at this speed will be around 32.
Current flash units (2010) often have much lower manual numbers in HSS mode than in normal mode, even at speeds below the shutter time. For example, the Mecablitz 58 AF-1 digital flash unit has a guide number 58 in normal operation, but only 20 in HSS mode, even at low speed.
Maps Flash (photography)
Technique
Source of the article : Wikipedia
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