Measuring density value of colour negative - forming colour spectrum of light passing through negative and weighting individual wavelengths using liquid crystal attenuators whose transmissivity corresponds to sensitivity of printing material

摘要

The method involves matching the spectral sensitivity of a measurement device to the spectral sensitivity of a colour printing material and splitting the light passed through the negative into at least one colour spectrum using a spectrometer. The light intensity values of the individual wavelengths are weighted according to the spectral sensitivity of each material and summed. Liquid crystal controllable light attenuators (12a) are located at positions on the spectrum. The transmissivities of the devices are controlled according to the copier material's sensitivity in the corresp. wavelength region and the thus weighted light intensities per colour are separately detected and measured. ADVANTAGE - Esp. for use with negatives in three colours to determine intensities of three colours with which to illuminate original. Higher light intensities can be measured and number of computation steps reduced.