The final area of consideration relates to the density map that is used for the stored output data. We did not however indicate the relative brightness of a tile containing a 2 with respect to one containing a value of 1 or 10. For this consideration, two of the infinitely possible density tables are interesting to study. Let us assume that a zero will represent a white of density 0.0 and that a 255 will represent a black of density 1.0. Also note that understanding the use of Density in the two tables is important.
Density is a system of describing numerically, perceived differences in brightness.
Table 1 can be referred to as a linear density table. This selection of table has a number of distinct advantages including that it has uniform accuracy over the entire range from shadow to highlight. If the output device were capable of reproducing it, one could display 256 equal steps in a step wedge using this table. This representation becomes especially advantageous when attempting to modify the tone of an image by brightening or darkening any area since accuracy is spread uniformly. Note that the perceptual change in density between a 1 and a 2 is equivalent to the change observed between 64 and 128.