While there are plenty of images of 19th Century and 20th Century composers, there are few of earlier ones, there are only two authentic portraits of Bach.
The images provided for these earlier composers are often taken from Wikipedia and in turn are taken from CD covers without checking their authenticity.
To give an example, there is no authentic portrait of John Dowland. Diana Poulton in her study of the composer has portraits of important figures in his life but for Dowland, just his signature. The garish portrait that appears in Roon has nothing to do with Dowland.
Is there any way of sorting out this issue ?