Reduction ratio
a = low reduction b = normal reduction (16x-30x) c = high reduction (31x-60x) d = very high reduction (61x-90x) e = ultra high reduction (91x- ) u = unknown v = varies

Specific reduction ratio

(Enter a 3-digit number with leading zeros e.g. 020; 
if unknown fill with '|||'; 
if single digit missing, replace by 'u')

Specific material designation
a = Aperture card b = Microform cartridge c = Microfilm cassette e = Microfiche f = Microfiche cassette g = Microopaque u = Unspecified z = Other | = no attempt to code

Polarity
a = Positive b = Negative m = Mixed polarity u = Unknown | = No attempt to code

Dimensions
a = 8 mm (microfilm) d = 16 mm (microfilm) f = 35 mm (microfilm) g = 70 mm (microfilm) h = 105 mm (microfilm) l = 3x5 in. (8x13 cm) m = 4x6 in. (11x15 cm) o = 6x9 in. (16x23 cm) p = 3 1/4x7 3/8 in. (9x19 cm) u = Unknown z = Other | = No attempt to code

Colour
b = Black and white (monochrom) c = Multicolored m = Mixed u = Unknown z = Other | = No attempt to code

Emulsion of film
a = Silver halide b = Diazo c = Vesicular u = Unknown m = Mixed emulsion n = Not applicable z = Other | = No attempt to code

Generation
a = First generation (Master) b = Printing master c = Service copy m = Mixed generation u = Unknown | = No attempt to code

Base of film
a = safety base: undetermined c = safety base: acetate d = safety base: diacetate p = safety base: polyester r = safety base: mixed t = safety base: triacetate i = nitrate base m = mixed base (nitrate and safety) n = not applicable u = unknown z = other | = no attempt to code