Beyond dispute is the fact that, after 1870 especially, photography played an increasingly important role in the spread of knowledge about art by way of illustrated books, art journals, and folios. To this extent, at least, photography was regarded by most people as a perfectly useful and efficient means of mechanical reproduction. Historian Edgar Wind notes: "That our vision of art has been transformed by reproductions is obvious. Our eyes have been sharpened to those aspects of painting and sculpture that are brought out effectively by a camera." It is only when it came to the question Is photography art? or, more precisely, Is photography an art on par with painting? that problems arose. For most painters, historians, and critics the answer was a resounding no. Historian Wind writes: "What precludes photography, as Croche put it, from becoming 'entirely art', although it may have something artistic about it, is the crucial surrender of the pictorial act to an optical or chemical agency which, however carefully set up and controlled by the photographer, must remain automatic in its operation."