Multigrade Filter Adjustments
Pick a contrast grade from 0 to 5; the calculator applies the filter factor.
Where to find it
Tools tab Darkroom Enlarger Multigrade Filter section
Summary
Eleven half-step grade chips (0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5) drive a multigrade filter factor lookup. Grade 2 is baseline (factor 1.0); softer grades (0 to 1.5) and harder grades (3 to 5) need longer exposures because the filters cut more light.
Detail
How it works
What it does
Tap a grade chip and the calculator multiplies your print time by the filter factor for that grade. Grade 2 is neutral (no change); grade 0 needs 2.5x the time; grade 5 needs 4x the time.
Why filters change exposure
Variable-contrast paper has two emulsion layers, one sensitive to blue light (high contrast), one to green (low contrast). Filters bias the enlarger light toward one layer or the other. Strongly biased filters (grades 0, 5) absorb more light overall, so the paper sees less light per second and exposure has to lengthen to compensate.
Half-step grades
Most multigrade filter sets ship in half-step increments. A 0.5 between two whole grades gives finer contrast control. The calculator snaps to the nearest 0.5 grade and looks up the filter factor for that step.
Picking a grade
A flat negative (low contrast scene, soft developer) wants a hard grade (3 to 5) to add punch. A contrasty negative (harsh sun, pushed development) wants a soft grade (0 to 1) to tame highlights and open shadows. Most negatives print well at grade 2 or 2.5.
Filter factor readout
Below the chip row, the Filter factor row shows the multiplier (for example x1.60 for grade 1 or 3.5). The final print time at the top of the modal already includes this multiplier, so you can read it straight off.