Karl Struss: B&W Special Effects with Filtration

From American Cinematographer, Two-Faced Treachery by George Turner (March 1999)

"The first time Jekyll changed, we used a technique I had devised years before to show the healing of the lepers in Ben-Hur [1926]. Everybody was using orthochromatic film then, which reproduced reds and yellows as black, and gave blue-eyed actors 'fish-eyes.' I had begun using panchromatic film, which is sensitive to all colors. The leprosy spots were red makeup, which registered when shot through a green filter, but when we gradually moved a red filter over the lens, the makeup disappeared. The Hyde makeup was also in red and didn't show at all when the red filter was on the lens, but when the filter was moved down very slowly to the green, Mr. Hyde appeared."

- Karl Struss, ASC

Jordan Cronenweth: Two Way Mirror Effect

From American Cinematographer, Cinematography for Blade Runner by Herb A. Lightman and Richard Patterson (July 1982)

"One of the identifying characteristics of replicants is a strange glowing quality in their eyes. To achieve this effect, we'd use a two-way mirror-- 50 percent transmission, 50 percent reflection-- placed in front of the lens at a 45 degree angle. Then we'd project a light into the mirror so that it would be reflected into the eyes of the subject along the optical axis of the lens. We'd sometimes use very subtle gels to add color to the eyes. Often, we'd photograph a scene with and without this effect, so Ridley would have the option of when he'd use it."

- Jordan Cronenweth, ASC