DAR, PAR and strange ratios.
 

Hey guys!

I have a question. I'm just starting to get my head around aspect ratios and how everything works... but still there are some things I just don't get. Any help with this would be very much appreciated.

Normal TV aspect ratio is 1.33, or 4:3, and yeah.. that seems all good for 640x480 for example. But if I would convert this to PAL land for a little while...

SD DV is 720x576. In square pixels this is 786x576 for everything to look right on screen, but this means a DAR of 1.3645?? A true 1.33 ratio would mean 768x576, but this in practice doesn't seem to fit the original footage.
Same thing is true for widescreen for instance. 16:9 which means 1.78. Again DV is 720x576. The PAR for widescreen is about 1.46, which means that in square pixels this would become 1048x576... but this again equals to DAR of 1.82 where you really want 1.78? Again... what you would want seems to be 1024x576 for a 16:9 relationship but this doesn't seem to fit the original image.

Where do I go wrong? Thx a lot!

Also.. why are widescreen computer screens 1.6? Shouldn't they be 1.78??