Answer:
The ratio of increment of illumination to background of illumination is called as weber ratio.(ie) ?i/i
If the ratio (?i/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.
If the ratio (?i/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.
If the ratio (?i/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.
If the ratio (?i/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.