Flash Photography Assignment

• Used in photography for artificial light
• Can be 1/1000 - 1/200 of a second long
• Used for iluuminating a dark scene, fast-moving objects, changing the quality
• The earliest flashes used flash powder (mix of magnesium powder and potassium chlorate), then it was the flash lamp invented by Joshua Cohen
• Flash lamp replaced by flash bulb, magneisum filaments were electronically ignited by contact witht eh camera shutter
• Other types of early flash technology are flash cube, magicubes, flashbar, flipflash
• Electronic flash using electronic circutry developed also
• Air-gap flash is an extremely fast flash (less than one microsecond) used more by scientists capturing fast moving objects like bullets tearing through light bulbs or batteries
• Multiple flashes can be used to find depth edges or create stylized images causing shadows in scenes
• Flash units can be expressed by t.5, which means the flash impluse is above .5 (50%) of peak intensity
• Flash LED illumination is used in camera phones becayse of their low voltage operation, higher efficiency, and extreme miniaturization
• Electronic flash units have compatibility issues with focal-plane shutters
• Fill flash describes the flash used to supplement ambient light in order to illuminate a subject close to the camera that would be in shade
• Bounce flash is directed onto a reflective suface, can look less articficial looking
•  Slave flash is set up away from the subject and camera, triggered by the light from the main flash
• Correction gels are used to change the color of the flash
• Using on-camera flash will give a very harsh light, which results in a loss of shadows in the image using an umbrella or softbox (the flash will have to be off-camera for this) makes softer shadows
• A typical problem with cameras using built-in flash units is the low intensity of the flash; the level of light produced will often not suffice for good pictures at distances of over 3 meters or so. 
• Dark, murky pictures with excessive image noise or "grain" will result. In order to get good flash pictures with simple camera an umbrella, and can even be used against sunlight, at short distance
• The "red-eye effect" is another problem with on camera and ring flash units. Since the retina of the human eye reflects red light straight back in the direction it came from, pictures taken from straight in front of a face often exhibit this effect.
• It can be somewhat reduced by using the "red eye reduction" found on many cameras (a pre-flash that makes the subject's irises contract)
• On some cameras the flash exposure measuring logic fires a pre-flash very quickly before the real flash. In some camera/people combinations this will lead to shut eyes in every picture taken
• Flash distracts people, limiting the number of pictures that can be taken without irritating them
• Photographing with flash may not be permitted in some museums since only assholes do that
• Flash equipment may take some time to set up may need to be carefully secured, especially if hanging overhead so it does not fall on anyone