Ilsted studied at the Royal Danish Academy of Fine Arts 1878-83 and exhibited from 1882.

In 1891, the year he also married, Ilsted’s sister married the painter Vilhelm Hammershøi and the two artists worked closely together. The same year both joined the progressive association Den Frie Udstillung (Free Exhibitions) and both, together with Carl Holsøe, became the leading Danish artists, painting quiet domestic interiors inspired by an admiration for Vermeer.

But only Ilsted was also a printmaker. His earlier prints were etchings. As his etchings became increasingly tonal, through use of crosshatching, from 1906 Ilsted focussed on mezzotint, a process little known in Denmark, and even visited England in 1913 to study and collect examples. On cream wove.