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Month: July 2016

Book review of “A textbook of photographic chemistry” by D. John and G. Field

In my crusade to learn more about photographic chemistry I visited the US, UK and German versions of Amazon’s second hand scene and went on a book buying spree. One of the books that I purchased is “A textbook of photographic chemistry” by D.H.O. John and G.T.J. Field, which was published in 1963. I bought my copy from for less than 9 euros in okay condition. The binding is reinforced with clear tape, the dust cover is missing and it contains some markings, but nothing that spoils it from being a decent read. Although it may be annoying to read…

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Reciprocity failure: the science

Lately I have been playing with the idea of trying some long exposures on film or direct-positive paper, but reciprocity law failure complicates shots that need much longer than a second of exposure. To explain why, answer the following question. When you close down the aperture by one stop, you can compensate for this by lengthening the exposure time by how much? … It probably didn’t take long to realize that you simply double the exposure time. However, chemical processes ongoing in the emulsion during exposure, makes the response deviate from the reciprocity law for very short or long(ish) exposures. In this article, I will introduce these processes…

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