[Tig] Nyquist/Fourier (was: new on the TIG wiki)

[Bob Friesenhahn]

On Mon, 14 May 2007, Jack James wrote:
>
> but pixels themseleves are just samples, there is limited value in
> reconstructing a perfect edge of a sample. in addition, ultimately the
> limiting factor is the eye, which has a rough resolution of 500x500.
> higher resolutions than 1000x1000 therefore only have an impact on the
> ratio of viewing distance/screen size.

I am 100% behind the explanation from Joe Owens since it matches my 
own understanding.

Note that actual resolution should be in lines or pixels per linear 
unit of measurement (e.g. pixels per inch).  An image of 500x500 
pixels produces a substantially different resolution on a small screen 
than it does on a big screen.  The resolution limits of the eye are 
best expressed as an angle (see 
http://en.wikipedia.org/wiki/Visual_acuity).

While the eye has limited detail definition within a given focal view, 
it has the ability to rotate in its socket and focus on a different 
area.  Therefore (as you say) the actual value of the increased 
image size is to allow the picture size to be increased.  However, I 
would remove the "only" clause since anyone who has experienced a high 
quality image on a small screen and a large screen at the same viewing 
distance will immediately tell you that it is like night and day.

Perhaps folks here would like to comment on the use of "deep focus" 
where most of the image is in focus.  This was used to great benefit 
in old films like "Seven Samurai".  While some directors say that 
shallow focus allows them to draw the viewer's attention to a certain 
part of the image, it seems that deep focus offers benefit to the 
viewer in that he/she can see detail in more of the image so that it 
feels more real.  With a deep focus image, the viewer may rotate his 
eyeball to look at detail in more areas of the image.  Comments?

Bob
======================================
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/