تويت
رؤية الغيب ..
الإضاءة ..
كتاب التصوير الفوتوغرافي المغلق
Seeing the unseen
At either end of the visible spectrum used to take conventional black and white or color photographs , images can be made within a band of short ultra - violet ( UV ) and long infra red ( IR ) wavelengths . UV light sources for photography include " black " fluorescent tubes ( which emit a weak , visible , purple light ) , mercury vapor lamps ( used by entomologists to attract night - flying moths ) and electronic flash . Gemstone suppliers sell portable UV lamps for examining minerals which fluoresce when they are subjected to UV light . These lamps can be used for photographing minerals .
All filmstock is sensitive to UV light , but special black and white and color films have to be used for IR photography ; the IR color film records objects in bizarre false colors . These films are so sensitive to fogging by light and heat that they have to be stored in a freezer and after thawing loaded into a camera in complete darkness . Filters used for taking black and white IR photographs may be red ( Wratten 25 ) or black ( 88A ) . Since the latter blocks visible light , it is impossible to focus the camera , which must be prefocused on a tripod ; even then it will not be precisely focused for long IR wavelengths . With black and white IR films , this problem can be overcome by adjusting the visible focus distance to the IR mark now printed on many modern lenses . But when a Wratten 12 filter is used with IR color film , much visible light reaches the film , so no shift in focus is necessary . Electronic flash ( covered with a Wratten 87 filter ) can be used as an IR light source for indoor color photography .
Ultra - violet light pattern
In visible light , an evening primrose appears as a uniform tone ( below left ) , but when photographed in ultra - violet light a dramatic pattern appears ( below right ) . I took this picture using an ultra - violet emitting mercury vapor lamp with a Wood's glass ( OX1 ) filter over the camera lens . This visually black filter cuts out so much light , an exposure increase of 12 stops is required . Lens Hasselblad 80mm + 0.5 Proxar Mag . on film * 0.25 Mag . on page × 1
◄ A fluorescing mineral I first took a piece of autonite in visible light ( left ) . Using a yellow filter , I then photographed the mineral in a darkroom as it fluoresced under black ultra - violet lights ( below ) . Lens Hasselblad 80mm + 32mm extension Mag . on film × 0.3 Mag . on page × 1
Fluorescent abstract
One day when I was looking at minerals beneath an ultra - violet lamp , I noticed that parts of my hands were faintly glowing . Moments before I had mopped up a yellow colored bubble bath solution which had spilled on the bathroom floor . I poured the remains into a Idish to check that it did indeed fluoresce . To take this picture , I bought a new bottle and squirted it in a random pattern onto yellow blotting paper . In visible light it was difficult to separate the yellow bubble bath solution from the paper , but as soon as I placed it beneath the black ultra - violet lights , it glowed brightly against the non reflective background which appeared black . I used a yellow filter over the camera to take the picture . Several weeks later , the pattern on the paper still fluoresced . Lens Hasselblad 80mm + 32mm extension Mag . on film * 0.3 Mag . on page × 2
الإضاءة ..
كتاب التصوير الفوتوغرافي المغلق
Seeing the unseen
At either end of the visible spectrum used to take conventional black and white or color photographs , images can be made within a band of short ultra - violet ( UV ) and long infra red ( IR ) wavelengths . UV light sources for photography include " black " fluorescent tubes ( which emit a weak , visible , purple light ) , mercury vapor lamps ( used by entomologists to attract night - flying moths ) and electronic flash . Gemstone suppliers sell portable UV lamps for examining minerals which fluoresce when they are subjected to UV light . These lamps can be used for photographing minerals .
All filmstock is sensitive to UV light , but special black and white and color films have to be used for IR photography ; the IR color film records objects in bizarre false colors . These films are so sensitive to fogging by light and heat that they have to be stored in a freezer and after thawing loaded into a camera in complete darkness . Filters used for taking black and white IR photographs may be red ( Wratten 25 ) or black ( 88A ) . Since the latter blocks visible light , it is impossible to focus the camera , which must be prefocused on a tripod ; even then it will not be precisely focused for long IR wavelengths . With black and white IR films , this problem can be overcome by adjusting the visible focus distance to the IR mark now printed on many modern lenses . But when a Wratten 12 filter is used with IR color film , much visible light reaches the film , so no shift in focus is necessary . Electronic flash ( covered with a Wratten 87 filter ) can be used as an IR light source for indoor color photography .
Ultra - violet light pattern
In visible light , an evening primrose appears as a uniform tone ( below left ) , but when photographed in ultra - violet light a dramatic pattern appears ( below right ) . I took this picture using an ultra - violet emitting mercury vapor lamp with a Wood's glass ( OX1 ) filter over the camera lens . This visually black filter cuts out so much light , an exposure increase of 12 stops is required . Lens Hasselblad 80mm + 0.5 Proxar Mag . on film * 0.25 Mag . on page × 1
◄ A fluorescing mineral I first took a piece of autonite in visible light ( left ) . Using a yellow filter , I then photographed the mineral in a darkroom as it fluoresced under black ultra - violet lights ( below ) . Lens Hasselblad 80mm + 32mm extension Mag . on film × 0.3 Mag . on page × 1
Fluorescent abstract
One day when I was looking at minerals beneath an ultra - violet lamp , I noticed that parts of my hands were faintly glowing . Moments before I had mopped up a yellow colored bubble bath solution which had spilled on the bathroom floor . I poured the remains into a Idish to check that it did indeed fluoresce . To take this picture , I bought a new bottle and squirted it in a random pattern onto yellow blotting paper . In visible light it was difficult to separate the yellow bubble bath solution from the paper , but as soon as I placed it beneath the black ultra - violet lights , it glowed brightly against the non reflective background which appeared black . I used a yellow filter over the camera to take the picture . Several weeks later , the pattern on the paper still fluoresced . Lens Hasselblad 80mm + 32mm extension Mag . on film * 0.3 Mag . on page × 2
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