Historians are happy to find plateaus in the flow of time at neat chronological intervals, such as "the turn of the century". If nothing else, it serves as a mnemonic device, or a euphonious book title. As this is written, we have passed such a marker in time, and it seems appropriate to review our perspective.

With a little rounding of dates photography can be said to have completed an era by the end of the 19th century. This era was marked by the first successful attainment of the long-sought permanent image of nature, and by the enthusiastic efforts of a multitude of individual inventors, many of them amateurs. As in so many fields this activity gave way in the 20th century to the trusts and combines of big business and big science.

In the 20th century the number of basically new processes is much smaller than in the 19th century. Not that progress has slowed; rather, it has accelerated, but it is of a different nature. We have seen the introduction of 35mm still photography (cinematography had its roots in the 19th century), and finally the end of the insidious nitrate film. Color photography, also rooted in the 19th, has reached dominance in amateur processing. Fast highly corrected lenses are commonplace, along with electronic light metering and a cornucopia of less fundamental gadgets. In the 19th century photographers proudly advertised "instantaneous" portraiture, meaning that exposure times were short enough that the human subject did not have to be propped up with a concealed support. Today "instant" photography means color prints from the camera in a minute - not, however, according to Webster's definition of instant as "an infinitesimal space of time"; for that, it appears that we must abandon chemistry.

A few years ago there was concern that the world would encounter a shortage of silver for photography in the foreseeable future, and research efforts were begun to find a substitute. At first these proprietary efforts were concentrated in the field of chemistry, until the computer revolution exploded. For a time it appeared that chemistry had been outflanked by solid state physics, and to a significant extent this has happened, particularly in video. Today silicon chips serve as the eyes in color television cameras, camcorders, and still cameras, generating pictures that are stored on magnetic or silicon media for instant (sic) playback without chemical intervention.

However, the outflanking has not decided the battle. As Tadaaki Tani concludes in his important 1995 survey [141], there are fundamental technical reasons to sustain our faith in chemical photography for many applications. As we approach a new era, the 21st century, the day of silver and wet chemistry in photography is definitely not over, but the time line is murky.

One source recently estimated that 66 billion photographs will be made this year. It seems likely that this number will increase as technology opens new doors, just as it did in the 19th century for the same reason. A more detailed prognosis would be extremely rash, given the unpredictable nature of invention. Progress is inexorable and merciless, and some of our present processes may one day be relegated to "revivals". But after 150 years the prospects for innovation are bright, though inspired amateurs and artists may not have the remarkable influence they enjoyed (and profited from) in the 19th century.