A bras cylinder tintmeter made by Alfred Watkins of Hereford who was for many years a leading manufacturer of meters. This meter was one of his most popular and was marketed from 1891 to 1907. The photographer could view light sensitive paper through the glas and judge light intensity by the time the paper took to darken. This kind of meter was in use until the early 1930s when photoelectric meters were introduced.
© National Media Museum / Science & Society Picture Library