Abstract: A photographic film unit comprises a support having coated thereon at least one photosensitive silver halide emulsion, said layer having associated therewith a dye image-providing material, a dye image-receiving layer, means for discharging an alkaline processing composition within the film unit and at least one layer containing at least one para-nitrobenzylidene dye-forming compound. Some of the para-nitrobenzylidene dye-forming compounds are a dark color at moderately and highly alkaline conditions and are colorless at neutral or only slightly alkaline conditions such as at ambient conditions.