Interchangeable slide-in module for the 4x5 series that allows continuously variable dialing of contrast grades for black and white printing. Dual filtration channels in one head. Channel one is calibrated for Kodak Polycontrast III RC and compatible papers (grades 0-5), channel two is calibrated for Ilford Multigrade III RC and compatible papers (grades 0-5). Memory-Lock white-light system for easy focusing. Automatic neutral density (ND) filter keeps exposure times constant throughout the contrast range.