> Density values are >absolute values, just like one foot is an absolute value. They have meaning >in and of them selves. Someone decided what the exact length of one foot is >(within a tolerance of course), as well as density values.
Just as a point of levity did not Einstein's theory of relativity call the notion that a foot would be the same under all circumstances in all locations (i.e. a universal absolute)? If so, why would it not apply to the lowly density measure as well as the "foot" as a unit of measure? :-) -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Austin Franklin Sent: Saturday, June 08, 2002 12:18 PM To: [EMAIL PROTECTED] Subject: [filmscanners] RE: Density vs Dynamic range - was: RE: opinions? Reviews? of Primefilm 1800 ? > Hi Tony, > > > Number of bits have two main roles. They do indeed represent the > > theoretical > > maximum density that a scanner could have if the electrical > > components were > > up to scratch and could use those bits to their full. > > Not true. You can represent ANY density by any number of bits. I can > represent an entire density range with two bits: > > 00 - at or below dMin > 10 or 01 - between dMin and dMax > 10 - at or below dMax BTW, that should be "at or ABOVE dMax"...sorry. > This is a completely valid encoding of density range. > > I have to run now, so I'll comment on the rest of your post later. > > Regards, > > Austin And...to add further to this, as I have a few moments... Density values are absolute values, just like one foot is an absolute value. They have meaning in and of them selves. Someone decided what the exact length of one foot is (within a tolerance of course), as well as density values. They mean the same thing everywhere...a density value of 1.6 means exactly that in La Jolla CA, as well as in Pascagoula, MS. Same with one foot. But, the tonal values out of a scanner are not the same everywhere, nor are they the same even between scans! The value 136 in La Jolla, CA...does not have the same tonality as the value 136 in Pascagoula, MS. Scanners are not calibrated TO anything, except themselves. That is why the data values you get from the scanner are not the same "density values". There is no direct correlation between them, unless you were to calibrate your scanner in the same way densitometers are calibrated (even that is insufficient, as the sensors used in film scanners have different characteristics than the sensors used in densitometers). Now, WHY would anyone in the first place say that number of bits has anything to do with density range...because they made some erroneous assumptions. Density range is stated in a ratio of "to 1" (:1), and a density of 3.6 is 10**3.6:1 or 3981:1 (and someone, at some time, decided what the density value of 1 physically is), which the number 3981 requires 12 bits to represent in the binary system, if you are going to represent every integer value from 1 to 3981...BUT...that's the rub...a value of 3981 from the scanner is NOT the same as a density value of 3.6 (3981:1), for the reasons explained above. And, no, they are not close enough for government work ;-) Regards, Austin ---------------------------------------------------------------------------- ------------ Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body