Martin Weberg wrote:
That's what I've been thinking. If the UV filter goes in both directions, which I assume, why do we get reflectance below 400nm? No UV wavelength's are emitted to the paper and no UV wavelength's reaches the measurement device.
Actually if you look closely at the filter, it only filters the light source. This make sense if you want to still measure reflectance below 420nm, as filtering the sensor will simply reduce sensitivity at those wavelengths. Graeme Gill.
