When light hits the of the film (through the lens), it exposes all layers equally, resulting in white overexposure. When light hits the back of the film (through the pressure plate or a broken seal), it must travel through the thick, orange/brown acetate base. This base acts as a filter, removing blue and green wavelengths. The only color left to burn into the emulsion is Red .
However, if you need consistency for professional work, A standard light seal kit costs $10 to $15. A roll of Portra costs $15. After just two rolls ruined by "light leaks RG," the repair pays for itself. light leaks rg