Minusgreen is a magenta correction filter used to reduce a green bias in a light source. It selectively changes the transmitted spectrum, shifting the source’s tint toward magenta.
Choosing a strength
Start with the measured or observed mismatch and test the required filter strength. A fractional correction may be sufficient. Applying full minusgreen to every fluorescent or LED source can create a new mismatch, because different lamps and settings have different spectra.
Practical example
If a practical reads greener than the key, test minusgreen on that practical where the fixture and filter arrangement permit it. Recheck both colour and exposure. The camera’s white balance affects the whole image, so correcting one offending source can be more useful than shifting everything together.
What correction cannot restore
A gel removes portions of the source’s output; it cannot add spectral energy that the lamp does not emit. Improving a neutral match therefore does not guarantee identical rendering of saturated objects. Allow for transmission loss and follow the filter and fixture manufacturer’s placement and temperature instructions.
Equipment examples
The Nanlite Forza 300B II provides electronic tint adjustment, an alternative worth testing when correcting that fixture instead of applying a physical gel.
Related terms
Plusgreen · Duv · CCT (Correlated Colour Temperature) · SSI (Spectral Similarity Index)
References
LEE Filters: green and magenta correction filters · Aputure: colour modes explained