preserving frame as much as possible (clip & zoom)

[ apologies if this double-posts.  i tried to post through gmane but
nothing showed up.  didn't even get the regular gmane first-time posting
confirmation, for whatever reason. ]

Hi,

I'm ripping a DVD to my PVR and I want to maintain as much of the
original frame as possible.  The Clip & Zoom tab shows me the original
frame is 720x480 with an Eff. ratio of 1.5 and a phys. ratio of 1.5
which makes sense.  The first clipping is 0/0/0/0.

Now I go to the After zoom and it's 720x408 with an Eff. ratio of 16:9,
phys. ratio of 1.76 after I reset the Width to 720 and used the Calc
height button to calculate a height of 408.

So the question is why this difference?  Why did 720x480 get transformed
to 720x408?  Certainly the second frame looks more in proportion than
the first (first frame looks too long -- everything is elongated
vertically).  Does this have something to do with square vs. rectangular
pixels on the "assumed" final display device or something like that?

If this is square vs. rectangular pixels (i.e. computer monitors vs.
televisions) what if my final display device is going to be a
television, just as the DVD was intended for in the first place?  Do LCD
televisions also have the rectangular pixels that traditional tube TVs
had?

b.

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