Old man wearing a top hat, c 1860.
© National Media Museum / Science & Society Picture Library
A collodion positive (ambrotype) of a seated man wearing a top hat, taken by Golum Hasan in about 1860. The collodion positive process (also commonly known as ambrotype) was popular during the 1850s and 1860s. An underexposed collodion negative on glass was backed with a black opaque coating to create a unique positive image.