Light is the basic element of photography, just as sound is that of music. A good photographer should be as familiar with light as the good musician is with notes and scales. Photography is, at its core, based on a very simple principle. An image of the world is captured by allowing a certain amount of light to fall on a piece of photosensitive material. Whether the photosensitive material in question is a silicon chip, silver film, glass plate or salted paper, this elegant little concept holds. Whether or not the light is shaped by the latest cutting edge in glass and coating technology, an old brass lens or indeed a humble pinhole, the same principles apply. The crucial questions of how much light reaches the photosensitive material and in what ways that amount may be controlled go to the very essence of photographic technique – the determination of exposure. “Reading the light” or “metering by eye” can be easily mastered with a little practice, yet most photographers leave this c
Van Dyke print on handmade paper from 4x5 negative For a little background to these overviews, see here . History: Introduced in 1889 by Arndt and Troos, the Van Dyke print is part of a group of iron based processes which draw on Sir John Herschel's work on the Argentotype silver-iron process developed in 1842. Negatives: A density range of about 1.5 is suitable. Sensitizer: Part A: 9gms ferric ammonium citrate (green) + 35ml water Part B: 1.5gms of tartaric acid + 35ml water Part C: 12gms silver nitrate + 35ml water In moderate light mix A, B and C (in that order) and age for a few days before use. The solution keeps well for about a year if kept in a cool, dark place. At times, owing to trace chemicals in various supplies of ferric ammonium citrate, the sensitizer may develop a muddy precipitate after about 2/3 of solution C is mixed. This can be allowed to settle and the clear sensitizer on top used, or adding about 2.5 gms more of tartaric acid can also dissolv