T3D Re: digital camera resolution

[michaelk@xxxxxxxxxxxxxxxxxx (Michael Kersenbrock)]

> Michael Kersenbrock wrote:
> > "Behind the lens and in front of the image sensor, many cameras
> > employ an optical prefilter -- a piece of quartz that selectively
> > blurs the image.  This prefilter conceptually serves the same
> > purpose as a lowpass audio filter.  Because the image sensor contains
> > fixed spacing between pixels, light wavelengths shorter than twice this
> > distance can produce aliasing distortion if they strike the sensor
> > (Notice the similarity to the Nyquist audio sampling frequency?).  A
> > similar distortion comes from taking a picture
> > containing  edge transitions that are too close together for the
> > sensor to accurately resolve them.  This distortion often manifests
> > itself as a color fringes around an edge (Figure 3) or as a series
> > of color rings known as a moire pattern. "
> 
> 
> Haven't heard of that concern before.  I wonder if this is somehow
> related to a single ccd imaging 3 colours.  Here aliasing is a concern
> because each of the three cells comprising a single "pixel" actually
> sample different spatial locations, hence the the next pixel wil not
> have it's red cell next to the previous pixel's red cell.
> 
> The systems I've worked on have used filters and separate images to
> provide colour.

Yes, that's one of the methods outlined in the article.  I'm  not too
sure the author or maybe editor of the article knew what they were
writing about (like I suspect the distance between pixels aren't
anywhere near light wavelength apart), so explainations might be
suspect, although that some cameras have fuzz filters is probably true
and that the explaination probably resembles what the author was told
with perhaps some swizzling of the buzz words here and there.

It also mentioned that some of the higher quality cameras didn't have
the filter.

Mike K.


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