On Wed, Oct 09, 2013 at 09:53:52AM -0700, Godfrey DiGiorgi wrote: > Aliasing occurs regardless of how close together the cells are because the > cells are discrete. This kind of aliasing is a function of discrete > mathematics.
I'm afraid that I left my discrete math textbook at home, and it has been 30+ years since I took the upper division classes in digital signal processing, so I'm a bit rusty.... but there is a big difference between sampling that takes the average over an interval and sampling that only samples at an instant in time. For example, if you have a 1 KHz sinusoidal signal, and take an instantaneous sample every 16.666mSec I think that you would get a very different waveform than if you integrate the input over those 16.666mSec. Since the integral will vary a small amount, dependng on where you are on the cycle, I can see that some aliasing would occur, but it's my understanding that AA filters do something similar, although integrating by continuous sampling is more of a boxcar finite impulse response filter, and the AA filters on sensors would be gaussian finite impulse repsonse filter. In any case, the bayer filter causes the boxcar filter integration to be discontinuous, 1/4 of the time for red and blue, and 1/2 the time for green. And that is assuming that all of the sensor surface is collecting data (photons). > G > > On Oct 9, 2013, at 9:08 AM, Larry Colen <[email protected]> wrote: > > > It seems to me that if you had a rear illuminated sensor, with no space > > between the pixels, and it had no bayer filter, then aliasing/moire would > > not happen, because the light value would be averaged over the whole sample. > > > > It's the discontinuous aspect of what is effectively three overlayed photos > > that is causing the aliasing. > > > > Is this correct? > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- Larry Colen [email protected] http://red4est.com/lrc -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
