Black and White Contrast Filters

Black and White Contrast Filters

Objective

To increase contrast between two colors that would normally photograph as nearly the same shade of gray using black and white film.

Light Information

White light is made up of a mixture of red, green and blue (primaries). In theory, red, green, and blue light sources simultaneously projected on the same area will be white. Red and green light mixed together makes yellow. Green and blue light mixed is cyan. Blue and red light mixed is magenta.

Light Transmission Law

The filter transmits its own color (lightened in the print) and absorbs (subtracts) is complementary color (darkened in the print).

Filter Color	Filter Designation	Absorbs (Darkens)	Transmits (Lightens)
Red	25A, 29	Blue & Green -- Cyan	Red
Blue	47,47B	Red & Green -- Yellow	Blue
Green	58, 61	Red & Blue -- Magenta	Green
Magenta	CC50M	Green	Red & Blue -- Magenta
Cyan	CC50C	Red	Green & Blue -- Cyan
Yellow	8, 15	Blue	Red & Green -- Yellow

Selecting Black and White Films and Filters to
Obtain Contrast Between Colors

Objective

To increase contrast between two colors that would normally photograph as nearly the same shade of gray using black and white film.

Films

Panchromatic films (T-MAX, PLUS-X, etc.) are blue, green and red sensitive. Colors are shown in varying shades of gray.

Orthochromatic films (KODALITH) are blue and green sensitive only. Red will appear black in a black and white print.

Desired Photographic Result	Panchromatic Film	Orthocromatic Film
Blue as Black	Red (25, 29)	Green (58, 61)
Blue as White	Blue (47, 47B)	Blue (47, 47B)
Blue-green as White	Cyan (50C)	Cyan (50C
Blue-green as Black	Red (25, 29)	Blue (47, 47B)
Green as White	Green (58, 61)	Green (58, 61)
Green as Black	Red (25, 29) or Blue (47, 47B)	Blue (47, 47B)
Orange as Black	Blue (47, 47B)	None
Orange as White	Yellow (15) or Red (25, 29)	Not Possible
Red as White	Red (25, 29)	Not Possible
Red as Black	Blue (47, 47B)	None
Violet as White	Blue (47, 47B)	Blue (47, 47B)
Violet as Black	Green (58, 61)	Green (58, 61)
Yellow as Black	Blue (47, 47B)	Blue (47, 47B)
Yellow as White	Yellow (15)	Green (11)
Yellow-green as White	Green (11, 13)	Green (11)
Yellow-green as Black	Blue (47, 47B)	Blue (47, 47B)

NOTE: As colors of objects are hardly ever "pure," the effects described are never perfect but the direction indicated is correct.