ah.. i see.. and we need some equipment/software to find out the range?
Dmax its the maximum density a sensor can differentiate..actually what we are more interested in is the dynamic range of the sensor. Given pure white and pure black and with steps in between, how many different steps can the scanner sensor differentiate before it just lumps it as pure black or white..
So in this sense, there should be a Dmin value to determine the minimum density before it clips to white..
Problem is that manufactures don't publish this data..and even if they do..they add a lot of "salt" to the values..so this makes it hard to determine the actual capabilities of different scanners in the market and of the scanner itself..
Note: this is also applicable to dslr sensors..except it is not as crucial when compared to scanning..