A fast and easy psycho-physical procedure to adjust luminance and achromatic contrast in conventional video display terminals (VDT)
AMLA (achromatic measurement and luminance adjustment) was applied to a group of 21 normal (non-colour blind) and a protanope. This method allowed the selection and measurement of relative luminance with chromatic and achromatic stimuli, to produce an easy and cheap production-measurement of achromatic contrast in VDT. The basis of AMLA are cheap luxometers can measure achromatic stimuli
relative luminance with the same precision that high quality photometers (this fact was confirmed). AMLA use a simple psychophysical task to determinate luminance equivalencies
between achromatic and chromatic stimuli. This task requires the adjustment of the luminance of an achromatic background to reduce the legibility of some coloured text. The normal subjects adjusted luminances very similar those presented. The protanope observer made adjustments: (1) as expected from his pathology and (2) significantly different from the normal subjects. These results showed that AMLA can be used to adjust screen contrast by observers with special needs.