Short throw with high zoom vs long throw short zoom

[Posh Bloke]

Finally getting round to ceiling mounting the PJ and I can't work out in my head which is the better option for siting the PJ away from the screen.. Should you go for a short distance with the zoom set to max or further away and zoomed out.

Plus points for close up are I guess brighter image but against is the fact that the centre and edge of screen to lens distance differences are exagerated and a nagging feeling that the extra magnification maybe could cause inacuracies.

Plus for further away is the whole screen area is much the same distance from the lens but against is the potentially lower light levels reaching the screen.

Oh and to add to the equation I also use some lens shift on the Z2.

Any clever technical types out there who could offer their opinion? Yes I know I could try both and see but in practice by the time you've moved evrything and realigned to the screen it's hard to remember what the previous set up was really like.

[Jules]

I'd go for further away, as this will minimise the chance of hot spotting.

Also, the closer the projector is to the screen, the sharper the angle of reflection is. With a high gain screen, this can cause problems too.

[Gary Lightfoot]

Further back means less light scatter within the lens and theoretically better contrast because the beam is tighter (through th ecenter of the lens rather than near the edges). It will also reflect the light straight back from the screen rather than out towards the walls so can reduce those reflections.

Gary.

[RTFM]

Further back is definitely better as per the points made above.
In addition there is less refraction of light as it passes through the lens which will result in less chromatic aberation and less pin cushion or barrel distortion.

Jeff