I agree with Todd’s assumptions above about texture (optical or real) and that it can be on a microscopic level but it doesn’t have to be.
Thinking of a flat finish paint surface you have to view it as a rough surface comprised of the color the pigments in the paint mix. Light striking a craggy surface (microscopic) is thrown out in a nearly 180 degree viewing cone equally.
Higher sheen paints or the addition of things like poly smooth the surface and in addition add specularity (mirror-like) quality. Higher gain lesser viewing cone as a result, and yes hot spotting if taken to an extreme.
What Todd noted as mild image drop off to the sides IMO is the first beginnings of a hotspot.
Putting the metallic (pearl) into the topcoat causes the optical texture. Optical texture to me is embedding all these tiny mirrors (the metallic) into the paint or the poly and they act just like the rough craggy paint surface of the flat paint but do so while maintaining the specular gain of the poly. And evening the brightness of the image across the screen.
I believe and have believed in the merits of these metallic improved paints for a very long time and Todd’s MaxxMudd experiment thread pointed out how this all works. (at least to me)
The bottom line for me has always been at what point they became necessary and to whom. If your projector is underpowered for the task at hand (too large a screen, too much ambient light etc.) then they can make a huge difference over something much simpler to do. What they will do is improve the efficiency of the screen surface and in doing so allow one to return the same FL image off a darker screen, and when dealing with ambient that’s always a good thing.
I debated long and hard with some of our now missing friends that this is most likely what is taking place in the metallic paints and that they should still see the benefits of the gray with the improvements of the metallic. This went back a year at least and I thought was becoming realized in the thread Mr. Sennin linked above.
People are of the assumption that it takes a special screen surface to bring out the best of a projected image. I don’t believe that to be true. What all these special surfaces do is compensate for deficiencies. And all theaters have some degree of deficiency. It’s understanding what they are and how and when they apply to you that makes all the difference.
The above post is subject to IMHO. And could be wrong…..
Below is a close up image of my screen surface. Not optical texture but still texture at a sub pixel size it’s painted with a paint that has no metallic but has a top coating that has a degree of specular gain.
extreme close up