The second type, known variously as a multiple back, repeating back or drop back camera, still exposed the images one at a time but used a sliding holder for the filters and plates which allowed each filter and the corresponding unexposed area of emulsion to be quickly shifted into place. German photochemistry professor Adolf Miethe designed a high-quality camera of this type which was commercially introduced by Bermpohl in 1903. It was probably this Miethe-Bermpohl camera which was used by Miethe's pupil Sergei Mikhailovich Prokudin-Gorskii to make his now-celebrated color photographic surveys of Russia before the 1917 revolution. One sophisticated variant, patented by Frederic Eugene Ives in 1897, was driven by clockwork and could be adjusted to automatically make each of the exposures for a different length of time according to the particular color sensitivities of the emulsion being used.