In optics, density is the transmittance of an optical element for a given length and a given wavelength.
For a sample of constant thickness, it is expressed as the logarithm of the ratio of light transmitted through the sample.
In black and white transmission densitometers, the wavelength response is visual( y(λ) ) sensitivity.
e.g. Transmittance(I1/I0) Density
1 100% 0.00
10-1 10% 1.00
10-2 1% 2.00
10-3 0.1% 3.00
10-4 0.01% 4.00
10-5 0.001% 5.00
10-6 0.0001% 6.00
