Re: Digicam

[Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>]

In article <FAEBJHPJNNGCAGDNGLNPEEKDEIAA.gsellani@accesscom.com>, gary 
<gsellani@accesscom.com> writes
>Your explanations would be much clearer without the "convolution in one
>domain is multiplication in the other domain" statement (which we know
>anyway).  Your diatribe on the effects of MTF is just an extension of the
>idea that "pixels have width", which was something I agreed with from the
>beginning.
>
Yes, presumably that is why you first wrote:
"the pixel should not have size" and then followed it up with:
"it is true that imaging does not have a pre-filter, but so what"

The fact of the matter is that the pixel size and shape DOES form a 
pre-filter and there is NO need for the pixels NOT to have a size - even 
under ideal conditions.

If you knew that, why did you contradict it?  What you term a diatribe 
was actually an attempt to explain something which you had clearly 
stated in error - TWICE!!

>Now doesn't the unsharp mask (to what ever degree), reduce the effects of
>the "width" (or in reality sharing information) between pixels.
>
Certainly, an unsharp mask compensates, to a limited degree, for the 
pixel filter, however your original postulation was that this was 
somehow related to the analogy of DAC reconstruction in audio:
"Going back to the audio analogy, if you take the  sample impulses and 
play them back on a DAC making staircase waveforms, the high frequency 
response will be incorrect".

The hold function of the DAC is only ONE representation of the sampled 
output and by no means unique.  Further, as I made clear in my original 
response to your analogy, in order to compensate for any DAC hold 
function, you must have sufficient resolution to define the detail of 
that hold function - that can only be done by interpolation, since the 
individual samples themselves are insufficient.  This is, if you like, 
much more analogous to an oversampling DAC and noise shaping digital 
filter.
-- 
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
-
Turn off HTML mail features. Keep quoted material short. Use accurate
subject lines. http://www.leben.com/lists for list instructions.