T3D Re: digital camera resolution

[John Ohrt <johrt@xxxxxxx>]

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.
--
John Ohrt,
Toronto * Ontario * Canada



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