Coghill, Sir John Joscelyn (1826–1905), 4th baronet and photographer, was born 11 February 1826, eldest son of Sir Josiah Coghill, 3rd baronet and vice-admiral, and his second wife, Anna Maria, eldest daughter of the Rt Hon. Charles Kendal Bushe (qv), lord chief justice of the king's bench in Ireland. John Coghill had a brother and six sisters from the second marriage and two half-sisters from the first marriage. He was educated at Rugby and served in the 59th Regiment.
Coghill lived at Belvedere House, Drumcondra, Dublin, and took a special interest in photography in the early 1850s, when wet-plate photography and a number of photographic paper processes became available to amateur photographers. He was present at the inaugural meeting of the Dublin Photographic Society (1854–8) on 1 November 1854 and was elected honorary secretary. He served a term as president and three terms as vice-president. In May 1858 the DPS changed its name to the Photographic Society of Ireland and amalgamated with the fine arts section of the RDS.
Coghill was one of the most travelled members of the DPS, having been in Germany and Switzerland in 1855 and in Switzerland again in 1857. In 1858 he and another member, Capt. Robert Henry, photographed in Spain, Portugal, and Gibraltar. Coghill imparted his knowledge and experiences of travel photography to the DPS in two lectures (November 1857, January 1859). In short, his advice was: stick to one photographic process, preferably the wet-plate, work from packs of materials weighing no more than thirty pounds (13.6 kg) (which should last six days), seek official permission to photograph public buildings, and, if crowds gather when a camera is taken out, do not show irritation, but encourage them to be your ally rather than your enemy.
The amalgamation with the fine arts section of the RDS was not happy. In May 1858 Henry McManus, RHA, headmaster of the school of art in the RDS, delivered a lecture on art in which he pointed out that the artist's craft could not be superseded by mechanical means. The artist's hand required the guidance of intelligence, McManus said, and this action could not be imitated by the use of machinery, however ingeniously contrived. Coghill differed with McManus on this occasion, and later in the year (November), when he replied more fully in a lecture at the RDS, Coghill described how photographers should study and reflect on art principles and not be mere servile copyists. He believed that photographers should use their intellect, taste, and judgement on the subject matter in front of the camera lens and so raise their photographic work from the mechanical to the sphere of art. He was influenced by the published ideas of a contemporary artist, James Duffield Harding. McManus was unrepentant and in 1862, in lectures to the Dublin Mechanics Institute, he continued to state that photography was not art, but merely the combined result of chemistry and mechanism.
Coghill left Dublin in 1860 and moved to Castletownshend, Co. Cork, where he continued his interest in photography. Throughout the 1860s he was a member of the Amateur Photographic Association in Britain, winning prizes on a number of occasions. As chairman of the photographic committee of the Dublin International Exhibition (1865) he was credited with the success of the photographic section, the adjudicators of which were Antoine Claudet and Peter le Neve Foster, both of whom had come from Britain. He exhibited in the 1870s in the APA in Britain, and exhibited for the last time in 1874, when he had nine photographs accepted in class one and was a prize-winner. In the 1870s, at his home, Laputa, in Castletownshend, he had a photographic darkroom where he taught photography to the next generation of his family and other relatives, including indirectly Edith Somerville (qv) and her sister Hildegarde, Coghill's daughter-in-law. His early photographic work is held by his family. He died on 29 November 1905 at his home in Castletownshend.
He married (1 February 1851) Katherine Frances, second daughter of the 3rd Baron Plunket, and had, with other issue, three sons, the eldest of whom, Nevill Josiah Aylmer, VC, lieutenant in the 24th Foot, was killed in action in the Zulu war at Isandhlwana, saving the colours. He held the official posts of DL and JP for Co. Dublin, and was high sheriff in 1859, the year he succeeded to the title.