Stanhope (optical bijou)

[1] The main disadvantage of Dancer's method was that the viewing of the microphotographs required a microscope which was at the time an expensive instrument.

[1] In 1857 René Dagron solved the problem by inventing a method of mounting the microphotographs at the end of a small cylindrical lens.

[1] Dagron also designed a special microphotographic camera which could produce 450 exposures approximately 2 by 2 millimetres (0.079 in × 0.079 in) on a 4.5-by-8.5-centimetre (1.8 in × 3.3 in) wet collodion plate.

[9] That same year, Dagron displayed the devices at the 1862 International Exhibition in London, where he received an "Honourable Mention" and presented them to Queen Victoria.

[10] In 1864 Dagron became famous when he produced a stanhope optical viewer which enabled the viewing of a microphotograph 1 square millimetre (0.0016 sq in), (equivalent in size to the head of a pin),[11] that included the portraits of 450 people.

[6][11] In the early twentieth century Eugène Reymond took control of Dagron's Stanhope lens factory in Gex, France.