Material specifications: 100% high quality optical resinOptical properties: 0.3 optical density, 50% of light transmittance in the darkest area, 1F stop light reductionOptical density tolerance: +/- 1% Dimensions:Dimensions tolerance: +/- 1%Stacking capability: Very Good.Generally about REVERSED GRADUAL ND filters/usage:REVERSED
GRADUAL ND filters have various density throughout filter space (soft
transition from light to dark then hard transition fromdark
to light). It means that light incoming to camera is reducing
gradually. This is very useful in situations where some of parts of the photography are overexposed (too much bright sky - especially on sunsets and sunrises).REVERSED GRADUAL ND filters are able to use with full or gradual filters in stacking mode.Density in stacking mode example: ND2 filter + ND4 filter is equal to ND8 filter (density is multiplied).