. The book of photography; practical, theoretical and applied. known underthe name of solarisation or reversal. Forinstance, a -greatly over-exposed film, ondevelopment, produces a positive insteadof a negative. It has been shown bynumerous investigators that the . latentimage behaves in a most peculiar mannerunder prolonged exposure. Up 4o a cer-tain point it gradually gains in intensityand then slowly disappears. It againreaches a certain degree of intensity,gradually diminishing a second time, andso on. In this connection, the followingfacts, due for the most part to Abney, areinteresting:
. The book of photography; practical, theoretical and applied. known underthe name of solarisation or reversal. Forinstance, a -greatly over-exposed film, ondevelopment, produces a positive insteadof a negative. It has been shown bynumerous investigators that the . latentimage behaves in a most peculiar mannerunder prolonged exposure. Up 4o a cer-tain point it gradually gains in intensityand then slowly disappears. It againreaches a certain degree of intensity,gradually diminishing a second time, andso on. In this connection, the followingfacts, due for the most part to Abney, areinteresting: Solarisation is facilitated bya preliminary exposure to diffused, day-light, by the action of powerful develop-ing solutions, and by treating the platewith a solution of some oxidising agent be-fore exposure. According to Abney^ at-mospheric oxidation is essential in pro-ducing solarisation. • , Difficulty of Explaining Reversal. It must be confessed that it is extremelydifficult to attempt to explain, from eithera chemical or physical point of view, the i. ^ l^^K Hi m JmJ H ^^E^^^^Hfe^^l 1
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectphotography, bookyear
