Archived posting to the Leica Users Group, 2002/02/10

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Subject: Re: [Leica] RE: Digital and lens resolution was Re: APD out
From: Mike Quinn <mlquinn@san.rr.com>
Date: Sun, 10 Feb 2002 18:34:43 -0800

Jim Brick wrote:

> You must 
> have a sampling rate at least four times the data rate.

Nice explanation,
Here are some diagrams I use to explain it to myself:

Twice the data rate is good enough for black & white.

Example:
Pixels: PIXELA--space--PIXELB--space
Sample:   1       2      3       4

So if each pixel can differentiate shades of gray, resolving two bits
requires four samples (twice the number of pixels).

If it takes four pixels (instead of 1) for each color bit, then:

          space  PIXEL2A  space   space   space   PIXEL2B   space   space
Pixels:  PIXEL1A  space  PIXEL3A  space  PIXEL1B   space   Pixel3B  space
          space  PIXEL4A  space   space   space   PIXEL4B   space   space
Sample:     1       2       3       4       5        6        7       8

So for color, resolving two bits requires 8 samples (four times the number
of pixels).

Which, of course, is just what you said.


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