Ilford Multigrade 3.5x3.5
The twelve MULTIGRADE filters are numbered 00-5 in 1/2 steps, with the lowest filter number corresponding to the softest contrast. Filters are available in sets of filters 8 . 9x8 . 9cm (3 1/2x3 1/2 inches) and 15 . 2x15 . 2cm (6x6 inches). They can be used above or below the lens and can be cut to fit the enlarger filter drawer. Filter sizes 30x30cm (11 . 8x11 . 8 inches) are available to special order.
MULTIGRADE filters are very easy to use: no complicated calculations are needed when changing from one filter to another. The exposure time for filters 00-3 1/2 is the same; that for filters 4-5 is double.