AVS Forum banner
Not open for further replies.
1 - 1 of 1 Posts

· Registered
14 Posts
Discussion Starter · #1 ·
Folks! I'm positing a theory here for feedback/corroboration.

What I've noticed is that one of the key PJ/PQ factors in front-projection that I haven't seen mentioned anywhere is what I call "Screen Flatness/Smoothness."

"Flat" means no waves, ripples, and perfectly perpendicular to the projector beam. Any variation from idealized Flat means slightly different focus, different dispersion, possibly different gain. This is why Fixed screens are generally better than tensioned, which are . in turn, better than roll-ups.

"Smooth" means no texture or surface irregularities, i.e. perfectly flat at a micro-scale. Variations from smooth cause all the same problems as above, but at a smaller scale.

My theory is that any variations from Perfect Flat and Perfect Smooth cause CUMULATIVE[?] distortions in the image that result in dull 2D viewing that we have all gotten used to. The resulting image is generally correct, but its missing some key qualities that are further exacerbated by the large projected size that even HDTV resolutions don't quite overcome. SO, the flatter screen [at macro scales] AND the smoother screen [at micro scales] results in a better picture in terms of depth, focus, contrast, "snap", "3D-ness".

I think this is probably very similar to THD [Total Harmonic Distortion] in the audio world. Some of the things we subjectively like about direct-view CRTs are probably caused by the very smooth/flat inner surface of the CRT! Same with Plasma, LCD and to a lesser extent RPTVs...they all have a controlled, micromachined surfaces to display the image that those of us with front projectors lack.

Ideallly, I believe that projection screen surfaces should be held to similar tolerances as lenses & mirrors. [For those of you who are amateur astronomers, U know the startling visual difference a high quality eyepiece makes. A mirror finished to 1/16 wave blows away one that has no specified tolerance.]

Background: I built a hardboard 6x10 screen with Behr UltraWhite Paint. I experimented over the last 2 years w/ Flat, Eggshell & Satin. [many coats of paint w/ many sandings in between. I'm down to 200 grit sandpaper!] I also tried the infamous blackout cloth, Parkland Polywall and everything else except Ken's Goo. I also have samples of all Da-Lite & Stewart screens. To make a very long story short, I stayed with my DIY screen [I'm projecting w/ Sony 10HT], but my favorite commercial screens are the smoothest ones like CinemaVision and Pearlescent. All the textured, ribbed and beaded ones looked very disappointing to me [but at the time, I didn't know why...] The blackout cloth looked very muddy to me, again, due to the rather coarse texture of the fabric.

In a week or two I will be switching to 5x10 Parkland Polywall, which I find superior to my DIY screen. I finally decided that the difference is in the smoothness and flatness of the Polywall over any other screen material [so far! ;-) ]

So...what do U guys think? Anybody else have same observations? am I off my rocker?

1 - 1 of 1 Posts
Not open for further replies.