We finish our journey with a series of images offering a very peculiar sort of detail: each of these photographs is made up of tiny, microscopic particles as a result of the photographic or printing process used.

In the case of the Autochrome, the granularity of the image was at the very core of its existence. Introduced by the Lumière brothers in 1907, the Autochrome was the first practical colour photography process. It was based on the additive colour system and involves covering a glass plate with a coloured layer with equal parts of red-orange, blue-violet and green starch grains. The resulting effect echoes the art of the pointillists.

In this early example, portraying a person dressed up like a fox, the larger coloured patches (the white trousers, green jacket and brown wallcovering) illustrate how the image consists of a mass of microscopic, coloured dots.

This photograph was produced using the gum bichromate printing process, involving an emulsion of gum arabic, ammonium or potassium and pigment spread on paper. A negative is laid over the emulsion and exposed to a UV light source. After exposure, the paper is placed in a series of water baths. To survive this process, the paper must be of a heavyweight type that can withstand repeated soakings. In the example on the right, the textured surface of the watercolour paper is clearly visible.

Another photographic technique resulting in granular images is the halftone process. Shown here is the eruption of Mount Pelée on the isle of Martinique. The scene was first photographed through a glass plate with fine lines printed at right angles. This resulted in an image broken up into tiny dots, corresponding to the openings in the screen. When printed, the dots create the optical illusion of continuous tones.

For many photography enthusiasts, the grain of early photographs is essential to the charm and the authenticity of the vintage image. Digital photography might lack the ‘grain’ of its analogue counterpart but it definitely helps to expose previously invisible details, adding to photographic impact. In this close-up of a Maori artefact, the granular background is as visible as is the structure of the wood from which the club is made.

This picture of a curved fragment of coloured glass not only proves it was part of a vessel or bowl but also reveals an intricate pattern made of red honeycombs and yellow spirals.

The tactile and technical mastery of early photographs, and the innovation of the digital medium today, both demonstrate the wisdom of French writer Marcel Proust when he stated that 'the real voyage of discovery consists not in seeking new landscapes, but in having new eyes.'