flash (photography)

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  • Flash (photography)

    The high-speed wing action of a hummingbird hawk-moth isfrozen by ash. The ash has given the foreground more illu-mination than the background. See Inverse-square law.

    A ash is a device used in photography producing a ashof articial light (typically 1/1000 to 1/200 of a second)at a color temperature of about 5500 K to help illumi-nate a scene. A major purpose of a ash is to illuminatea dark scene. Other uses are capturing quickly movingobjects or changing the quality of light. Flash refers ei-ther to the ash of light itself or to the electronic ashunit discharging the light. Most current ash units areelectronic, having evolved from single-use ashbulbs andammable powders. Modern cameras often activate ashunits automatically.Flash units are commonly built directly into a camera.Some cameras allow separate ash units to be mountedvia a standardized accessorymount bracket (a hot shoe).In professional studio equipment, ashes may be large,standalone units, or studio strobes, powered by specialbattery packs or connected to mains power. They areeither synchronized with the camera using a ash syn-chronization cable or radio signal, or are light-triggered,meaning that only one ash unit needs to be synchro-nized with the camera, and in turn triggers the other units,called slaves.

    1 Types of ash

    1.1 Flash-lamp

    Main article: Flash-lampStudies of magnesium by Bunsen and Roscoe in 1859

    1909 ash-lamp1903 view camera

    showed that burning this metal produced a light with simi-lar qualities to daylight. The potential application to pho-tography inspired Edward Sonstadt to investigate meth-ods of manufacturingmagnesium so that it would burn re-liably for this use. He applied for patents in 1862 and by1864 had started the Manchester Magnesium Companywith Edward Mellor. With the help of engineer WilliamMather, who was also a director of the company, theyproduced at magnesium ribbon, which was said to burnmore consistently and completely so giving better illumi-nation than round wire. It also had the benet of being asimpler and cheaper process than making round wire.[1]Mather was also credited with the invention of a holderfor the ribbon, which formed a lamp to burn it in.[2] Avariety of magnesium ribbon holders were produced byother manufacturers, such as the Pistol Flashmeter, whichincorporated an inscribed ruler that allowed the photog-rapher to use the correct length of ribbon for the exposurethey needed. The packaging also implies that the magne-sium ribbon was not necessarily broken o before beingignited.An alternative to ribbon was ash powder, a mixture of



    magnesium powder and potassium chlorate, introducedby its German inventors Adolf Miethe and JohannesGaedicke in 1887. Ameasured amount was put into a panor trough and ignited by hand, producing a brief brilliantash of light, along with the smoke and noise that mightbe expected from such an explosive event. This could bea life-threatening activity, especially if the ash powderwas damp.[3] An electrically triggered ash lamp was in-vented by Joshua Lionel Cowen in 1899. His patent de-scribes a device for igniting photographers ash powderby using dry cell batteries to heat a wire fuse. Variationsand alternatives were touted from time to time and a fewfound a measure of success in the marketplace, especiallyfor amateur use. In 1905, one French photographer wasusing intense non-explosive ashes produced by a specialmechanized carbon arc lamp to photograph subjects inhis studio,[4] but more portable and less expensive devicesprevailed. On through the 1920s, ash photography nor-mally meant a professional photographer sprinkling pow-der into the trough of a T-shaped ash lamp, holding italoft, then triggering a brief and (usually) harmless bit ofpyrotechnics.

    1.2 Flashbulbs

    Kodak Brownie Hawkeye with Kodalite Flasholder and Sylva-nia P25 blue-dot daylight-type ashbulb

    The use of ash powder in an open lamp was replacedby ash bulbs; magnesium laments were contained inbulbs lled with oxygen gas, and electrically ignited by acontact in the camera shutter.[5] Manufactured ashbulbswere rst produced commercially in Germany in 1929.[6]Such a bulb could only be used once, and was too hotto handle immediately after use, but the connement ofwhat would otherwise have amounted to a small explo-sion was an important advance. A later innovation wasthe coating of ashbulbs with a plastic lm to maintainbulb integrity in the event of the glass shattering duringthe ash. A blue plastic lm was introduced as an op-tion to match the spectral quality of the ash to daylight-balanced colour lm. Subsequently, the magnesium wasreplaced by zirconium, which produced a brighter ash.

    Flashbulbs took longer to reach full brightness and burnedfor longer than electronic ashes. Slower shutter speeds(typically from 1/10 to 1/50 of a second) were used oncameras to ensure proper synchronization. Cameras withash synch triggered the ashbulb a fraction of a secondbefore opening the shutter, allowing faster shutter speeds.A ashbulb widely used during the 1960s was the Press25, the (about 1 inch (25 mm) in diameter) ashbulb of-ten used by newspapermen in period movies, usually at-tached to a press camera or a twin-lens reex camera. Itspeak light output was around a million lumens. Otherashbulbs in common use were the M-series, M-2, M-3etc., which had a small (miniature) metal bayonet basefused to the glass bulb.The all-glass AG-1 bulb was introduced in 1958. Elim-inating both the metal base, and the multiple manufac-turing steps needed to attach it to the glass bulb, cut thecost substantially compared to the larger M series bulbs.The AG-1 (along with the M2) had a faster ignition time(less delay between shutter contact and peak output), soit could be used with X synch below 1/30 of a secondwhile most bulbs require a shutter speed of 1/15 on Xsynch to keep the shutter open long enough for the bulbto ignite and burn.[7]

    1.2.1 Flashcubes, Magicubes and Flipash

    Flashcube tted to a Kodak Instamatic camera, showing bothunused (left) and used (right) bulbs

    In the late 1960s Kodak improved their Instamatic cam-era line by replacing the individual ashbulb technol-ogy (used on early Instamatics) with the Flashcube. Aashcube was a single-use module with four ashbulbsmounted at 90 from the others in its own reector. Foruse it was mounted on a swivel mechanism atop the cam-era that also provided an electrical connection to the shut-ter release and a battery inside the camera. After eachexposure, the lm advance mechanism also rotated theashcube 90 to a fresh bulb. This arrangement allowedthe user to take four images in rapid succession beforeinserting a new ashcube.

  • 1.4 High speed ash 3

    Undersides of Flashcube (left) and Magicube (right) cartridges

    Flip ash type cartridge

    The later Magicube (or X-Cube) retained the four-bulbformat, and was supercially similar to the originalFlashcube. However, the Magicube did not require elec-trical power. Each bulb was set o by a plastic pin in thecube mount that released a cocked spring wire within thecube. This wire struck a primer tube at the base of thebulb, which contained a fulminate, which in turn ignitedshredded zirconium foil in the ash. Magicubes couldalso be red by inserting a thin object, such as a key orpaper clip, into one of the slots in the bottom of the cube.Flashcubes and Magicubes look similar but are not inter-changeable. Cameras requiring ashcubes have a roundsocket and a round hole for the ashcubes pin, whilethose requiring Magicubes have a round shape with pro-truding studs and a square socket hole for the Magicubessquare pin. The Magicube socket can also be seen as anX, which accounts for its alternate name, the X-Cube.Other common ashbulb-based devices were the Flash-bar and Flipash which provided about ten ashes froma single unit. The Flipash name derived from the factthat once half the ashes had been used up, the unit wasipped over and re-inserted to use the remainder.

    1.3 Electronic ash

    Electronic ash was developed after ashbulbs, and even-tually superseded them as prices came down; ashbulbsare virtually obsolete. A typical electronic ash unit haselectronic circuitry to charge a high-capacity capacitor toseveral hundred volts. When the ash is triggered by theshutters ash synchronization contact, the capacitor isdischarged almost instantaneously through a ash tube,

    producing a ash of very brief duration almost instanta-neously (i.e., the ash duration, often around 1/1000 of asecond, is shorter than the fastest practical shutter speed,and full brightness is reached before the shutter has timeto close appreciably). Synchronization of full ash bright-ness with maximum shutter opening was problematicalwith bulbs which took an appreciable time to ignite andreach full brightness; electronic ash does not have thesediculties. Electronic ash units are sometimes calledspeedlights or strobes in the USA.Simple electronic ash units are often mounted on or nearthe camera; many inexpensive cameras have an electronicash unit built in.

    Two professional xenon tube ashes

    Some lenses have built-in (ring-)ash lights for shadowfree macro photography, but there are also accessory ringashes available.In a photographic studio, more powerful and exiblestudio ash systems are used. They usually contain amodeling light, an incandescent light bulb close to theash tube; the continuous illumination of the modelinglight lets the photographer visualize the eect of the ash.A system may comprise multiple synchronised ashes formulti-source lighting.The strength of a ash device is often indicated in termsof a guide number designed to simplify exposure setting.The energy released by larger studio ash units, such asmonolights, is indicated in watt-seconds.

    1.4 High speed ash

    An air-gap a