stylistically, johnston's work is very similar to that of his friend copley, adopting similar poses and many of the stylistic characteristics of his early work; indeed, at least three of johnston's portraits have been misidentified as those of the younger artist in past years. his paintings also suggest the influence of joseph blackburn, who was painting in portsmouth at the same time he was there, although his style is more linear. he was generally comfortable working in a three-quarter length format; his greatest difficulty lay in attaching the sitter's head to the body. many of his poses and backgrounds are drawn from english mezzotints of the period. today two of johston's paintings may be found in the metropolitan museum of art, while one is owned by the connecticut historical society, and another is owned by the brooklyn museum of art.