Is Da-Lite HP an ALR tech?

There are different types of ALR screens optimized for rejecting ambient light coming from different directions. Since a retroreflective screen reflects any light that hits it directly back at the source it could be considered to be ambient light rejecting for any ambient light that doesn't come from the general area where the viewers are seated. For example, if you have a lighted lamp sitting right next to you an HP screen would reflect the lamp's light directly back at it and those sitting next to the lamp would get a big dose of that reflected lamp light.

With the extreme projection angle of a UST projector viewers are going to be far from the center of the viewing cone. Hypothetically if the UST projector is projecting an image up 45 degrees from the bottom of the screen then those seated back from the center of the screen are going to be sitting 45 degrees out of the prime spot in the viewing cone and much of the HP screen gain would be lost. The floor immediately in front of the screen where the projector is sitting (or ceiling if the UST projector is ceiling mounted) would be the center of the viewing cone getting maximum screen image gain.

Essentially a UST projector and retroreflective screen would make a poor combination because they would light up the floor or ceiling where the projector is mounted, creating objectionable cross reflections back onto the screen. Specialized UST ALR screens are very different from retroreflective screens for good reason.

To answer the original question:


The difference is that the Da-Lite High Power 2.8 uses tiny, spherical glass beads under a transparent and protective layer while the ALR screens (XY-Screen etc.) - AFAIK - use heterogenous crystals melded onto the surface of the screen.


In combination with an HP 2.8 the best placement position of a front projector would be right next the eyes and at eye level for maximum gain performance, because the spherical glass beads reflect back to where the projection light comes from.


As stated by the others, with a UST front projector the most light would also be reflected back to the position where it came from, but that's hardly the spot you'll expect to find the viewer or spectator.


For UST front projection there are special screens that reflect the UST projection light towards the viewers.


Please make certain to announce your possible intent to part with your High Power 2.8 in the corresponding thread here at the AVS as there is still considerable demand...