Abstract: Equidensity images can be produced directly on high contrast, thin emulsion, fine grain, silver halide process films, such as Kodak Technical Pan Film (RTM), given instantaneous outdoor camera exposure. Photographic development of the film in an aqueous alkaline solution containing a halogen- substituted hydroquinone such as 2-chlorohydroquinone, or 2-bromohydroquinone as developing agent, and thiourea, or a mono N-substituted derivative such as 1-allyl-2-thiourea, as "chemical solarizer", followed by fixation, produces continuous tone violet-blue (negative) and brown to olive-black (positive) images having applicability in semi-abstract artistic photography and in scientific photography.