720p or 1080i?
 

I will shoot a short movie with an fx-1, but I don't know which is better lower resolution and progressive scan (720p) or higher resolution and interlaced scan?

Apples & Oranges.

Progressive is always better because it captures the entire frame at once (at the sacrifice of some resolution). This is an acceptable trade-off for most people who shoot films because they generally like to shoot them in 24p.

I have just put my FX-1 on a tripod and pointed it out of my window to the street and trees outside. I recorded about 20 sec's of HD video while switching back and fourth to interlaced and progressive scan (25p - I live in PAL land)

Then I viewed it fullscreen (using VLC media player and windows media player) on my 24" Dell Full HD screen LCD and looked very, very closely to the brick wall and the trees (they had small details)

Well, I can tell you this: Only because I knew there should be a small difference and only because I know where to look for I could see a very, very minor drop in resolution when switching to 25p.

So if you like having 25p, just shoot 25p. Ofcourse you can de-interlace in post, but that will take a very, very long time and will force you to recompress once again - which is generally not a good idea, especially when working with mpeg compression!

The resolution trade off Scott mentions is in my opinion almost zero!

Progressive will give you the sharpest image when viewed at an identical framerate to an interlaced sequence. Interlaced will give you the smoothest motion. If you shoot interlaced, you can always dumb it down to 720 and get great results. If you shoot progressive in the FX1, you may not like the look of 30p/25p. Shooting progressive at 24/25/30 requires a little extra special care, and I'd recommend you spend a bit of time practicing before the big day.

like what kind of special care?

So.... If I use the cf30 setting ( no grandiose expectations of a film-out theatrical release )

things like this;

camera....
1/60th shutter
very slow pans ( if any )
avoid diagonal lines in scene

post...
(FCP) de-interlace footage or leave as is?

also... I'd love to here opinions on final file choices ( .mov? ) for interlace and progressive displays.... for instance.... I have a 720p projector and clients usually have plasmas, lcds, or crts....

no advice?

I understand.... there's a few workflow tricks I keep to myself as well.

so far.... my personal best results have been using nattress for a filmic look/cadence... then sizing down for my 720p projector.

Something deep inside me is afraid of the CF settings.... maybe eventually I'll get tired of all the plug-in ( nattress ) rendering times.... although, it does get me up out of the chair to stretch my legs.