VISUAL ARTS Garry Fabian Miller Arnolfini Gallery, Bristol; Michael Hue-Williams, London

The Arnolfini Gallery in Bristol is an appropriate venue for Garry Fabian Miller's exhibition Sections of England - The Sea Horizon. Not least because of the gallery's physical proximity to Clivedon, the place overlooking the Severn Estuary where this work was made, but also for the role that the Arnolfini has played in Miller's personal history.

It was there in 1976, aged 19, that he saw Artists Over Land: an exhibition that included work by Richard Long and Hamish Fulton and that led directly to his own experiments with landscape photography. Within months, Miller had begun work on the project that became The Sea Horizon and, within three years, he was back at the Arnolfini exhibiting some of the series in his first one-man show. That was 1979. Eighteen years on, a selection of the same photographs are back on the Arnolfini's walls.

The series consists of 30 pictures of the sea and sky taken from a fixed point on the roof of Miller's home looking westwards towards the south coast of Wales. They were taken at irregular intervals over a period of 18 months with several technical constants: same camera; same lens; same exposure; and the same position on the roof. The subject and the format are unchanged from one photograph to the next, but the variables of time, weather and Miller himself (choosing his moment according to his mood) determined the uniqueness of each image.

Some of the differences are slight: a layer of mist causing a subtle change in tone. Others are more dramatic: the sea, for example, shifting from solid blues and blacks to churning greys and browns. It all sounds very simple and yet the series' cumulative effect is a complex exploration of the nature of place and time and light, especially light. The most beautiful, to my eye, are the most blurry - the sea and sky conjoined in inky darkness, a dark mass fractured by a thin electric rim of horizon. Like paintings by Rothko, or the fields of colour painted by Turner in his proto-abstract explorations of light and weather.

When Miller first showed The Sea Horizon in 1979 he gave the exhibition an epigraph borrowed from Ben Nicholson: "Painting and religious experience are the same thing. It is a question of the perpetual motion of the right idea." Photography, too, Miller would add, but these days photography isn't quite a big enough word to describe what he does.

Then he worked with a camera and natural light, now his concern is more the nature of light itself. In recent years he has dispensed with the tools of lens and film in order to make work based on the principles of photography reduced to its simplest form. A process of image-making by passing light through his subject, a leaf perhaps or a glass of water, directly on to Cibachrome paper. The results are blindingly intense combinations of colour and light.

One of these recent Cibachromes is included alongside a second showing of The Sea Horizon at Michael Hue-Williams in London. Neither Hue-Williams nor the Arnolfini have had quite enough space to hang the complete series, but both selections are complete enough to reflect something of its extraordinary sadness and sense of place. Happily, all 30 have been included in a beautifully produced book published to mark the exhibitions.

Arnolfini Gallery, 16 Narrow Quay, Bristol (0117-929 9191) to 11 May; Michael Hue-Williams, 21 Cork Street, London W1 (0171-434 1318) to 10 May