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OK, I think I know Mark well enough that I can just say bollocks.

Representing a sample as a square (ie presenting a sine wave as a square wave) is introducing a whole series of (every alternate) higher harmonics which contribute absolutely NOTHING to the image.   This is really fundamental to understanding digital imaging.

                                                                               Guy

-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of Mark Cannell
Sent: Sunday, 15 April 2012 11:35 AM
To: [log in to unmask]
Subject: Re: Nyquist and Image size

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Hi Johannes

Sorry I disagree. You are recording an image. The point is that the pixels integrate over their entire face which is square so that this may be represented by square pixels perfectly faithfully. I have no idea what your analogy to the images of the sun through leaves has to do with this, the leavers are apertures. 

Cheers Mark


On 14/04/2012, at 6:43 PM, Johannes Schindelin wrote:

> Hi Mark,
> 
> On Sat, 14 Apr 2012, Mark Cannell wrote:
> 
>> That's a nice 'rant' but it does of course ignore the fact that many 
>> cameras have square pixels...
> 
> But it is not the square detectors of the camera you are recording. 
> There is a whole optical path up until then.
> 
> Pixels are not the physical dimension of the detector, they are an 
> abstract construct to describe what the number (or numbers) attached 
> to it
> -- the pixel value -- actually mean.
> 
> To say that pixels are square because the CCD is organized in a grid 
> is like saying that the spots the sun is leaving in a forest of trees 
> are as oddly shaped as the holes made by leaves through which the 
> sun's rays reach the soil.
> 
> Ciao,
> Johannes