JCO wrote:
JCOC> I can see from my 35mm 100 speed film
JCOC> negs that the 2400 dpi scanner I'm using
JCOC> is inadequate. Will 4800 ppi settle the
JCOC> matter once and for all or should I be waiting
JCOC> until 6400 or 7200 ppi scanners arrive to upgrade?
Strictly theoretically speaking, a 4800 dpi is only capable of
accurately sampling 47 lines per mm. This is derived from
Nyquist's sampling theorem, according to which you can only sample
half the frequency of the sampling machine:
4800 dpi / 2 / 2 dots per line / 25.4 mm/inch = 47 lines per mm
Of course in the real world you can get better or worse than that,
depending on how the sensor array aligns with the film pattern.
But to get the maximum of a 100 ASA film that usually peaks above
50 lpm at 1.6:1 contrast degree, you obviously need more than
4800 dpi.
Servus, Alin
