Bedste "Lens Throw" afstand?

Hi,

Assuming your screen a a fairly traditional white screen (not high contrast, or very high gain), then it won't matter much in terms of best viewing angles ("the viewing cone"), if you place it close.  

If you have a hi contrast gray screen or a very high power gain screen, the closer, the projector, the narrower the viewing cone, also the more roll of brightness to the corners.

With the Panasonic's zoom, the projector will be at its brightest, in the shortest throw position you are talking about.  (at the furthest position, you lose over 40% of the brightness).

Other aspects:

1.  no lens is at its absolute best a the closest or furthest points in its zoom range.  For that reason, I always suggest backing off about 10% if you can.  Is it that critical - no.

2.  There will be a little more bowing of the image (optics, lens shift related) as you work the range closer - this translates into a slight curving of the top and bottom of the image.  We're talking maybe an inch.  Every one deals with that to some point, no matter where in the zoom range, but the bowing is greater, the closer you go with the zoom.

3.  The more lens shift used, the more it too effects aspects - thus try to minimize lens shift if you have the option (ie. if you can mount the projector 1 foot above, or flush with the top of the screen - go flush, if all else is equal.

4.  Focus - it's tough enough to make a zoom lens that's sharp from center to corner, in terms of focus.  Because, the closer you are, the greater the percentage difference between the closest point on the screen (near center) and furthest (in your case, lower corners, is at its greatest.   Thus, further back you get a more even focus.  Again, the difference here,  too, is very slight

Those are the primary issues.  That said, other than the wrong screen type, the other points are very minor.  -art