You don't need four pixels to resolve two lines even if they're not black and white.
People are throwing around words like "Nyquist Theorem" without any actual understanding of what the Nyquist sampling theorem really says. Which is, roughly: if the input signal is frequency-limited to n Hz, it can be reconstructed without error from point-sampled data at 2n Hz. In other words, you need two samples per cycle of the highest-frequency component in order to be able to accurately reconstruct the input waveform. Point sampling at 128 pixels/mm is enough to reconstruct image data with frequencies of up to 64 cycles/mm. That's 64 line PAIRS per mm - a figure that's going to put a strain on the abilities of quite a few lenses. > you don't need four pixels to resolve two lines if one is black and one is > white. > > Herb.... > ----- Original Message ----- > From: "Alin Flaider" <[EMAIL PROTECTED]> > To: "Herb Chong" <[EMAIL PROTECTED]> > Sent: Wednesday, December 03, 2003 3:45 AM > Subject: Re: FA 31 mm 1.8 limited > > > > > > 128 pixels/mm translates to 64 lines/mm (you need 2 pixels to > > resolve a line). If the sensor resolution is 64 lines/mm, then its > > max resolving power is 64/2 = 32 lines/mm. > >
