Michelangelo Unterberger was trained in Cavalese with Giuseppe Alverti (1640-1716), a provincial painter with a considerable group of South Tyrolean pupils who later moved to Vienna (amongst them Paul Troger (1698-1762), to whom this picture has previously been attributed). After this initial training, Unterberger travelled to Venice where he may have worked under the supervision of Giovanni Battista Piazzetta. His exact progression is uncertain - he is recorded in Passau in 1725, but by 1737 he had certainly settled in Vienna, as he won first prize in life drawing at the Kunstakademie that year. He later became professor at the Kunstakademie and in 1751-54 its director. In the early 1750s when this picture was painted, Unterberger was at the height of his career, one of the most sought after altarpiece painters of the Habsburg Monarchy.
This picture is a study, a bozzetto, for the high altar of the Jesuit Church in Marosvsrhely in the vicinity of Trgu Mure, Rumania (K. Garas, loc. cit.). The church was founded in 1728 and consecrated in 1750. The high altar, commissioned by a Jnos Haller, was installed in 1754 (see, P. Kiss, Marosvsrhely trtnete, Marosvsrhely, 1943, p. 58). In the Historia Domus of the order the artist is described as the 'Apelles Viennensis', implying that he was regarded as pre-eminent amongst his fellow citizens. This makes improbable the identification of the artist as either Troger or Franz Anton Maulbertsch (1724-1796), who are also known to have painted altarpieces for churches the area. The commission for the altarpiece in Marosvsrhely was probably contemporary with the prestigious project for the altar of the Cathedral of Temesvr in Southern Hungary. That Church by Josef Emanuel Fischer von Erlach was consecrated in 1754 with its altarpiece already installed.
This sketch is a fine example of the Austrian tradition of the bozzetto painted by artists like Troger, Maulbertsch and Unterberger. This preliminary working method was influenced by Venetian artists such as Piazzetta and the Tiepolo family. Here, Unterberger plans with great care the symmetry of the composition and the palette. Angels enclose the figures of Christ and Saint John the Baptist in a semi-circle, capturing the light that contrasts with the dark background. There are two other oil studies for the composition; one is in the Nrodn Galerie, Prague (L. Slavicek, 'Na okraj vystavy Rakouskeho Barokneho umeni za sbirek Nrodn Galerie v Praze', Umeni, 1979, p. 545, fig. 6); the other was formerly with Galerie Sanct Lucas, Vienna. Based on the proximity of their compositions to the final altarpiece, the order in which the bozetti were painted was probably the Nrodn Galerie picture, the present picture, and lastly the Sanct Lucas picture.
As was often the case the artist might have re-used these three sketches for his Baptism of Christ in the Parish Church of Wulzeshofen (M. Krapf, op. cit., figs. 31-33, 36). Furthermore, Garas has pointed out the similarities with the picture of the same subject by Franz Sebald Unterberger, Michelangelo's brother, now in the Diocesan Museum in Bressanone, and with a picture by Franz Sebald in the Church of the Hospital in Bruneck (C. Garas, op.cit., p. 70).
The artist's style, which echoes the Venetian eighteenth-century Baroque had a considerable influence on artists of the following generation, for example Maulbertsch, who was to be appointed Professor at the Akademie in Vienna in 1759 (see the catalogue of the exhibition, Visionen des Barock, Hessisches Landesmuseum, Darmstadt, 1965).