Originally Posted by AnAx
Thanks for the info.
I have removed the screen so I can't take any new photos of it.
I choose the screen because it was recommended by the store and also because it had good reviews. That it was an ALR screen or not was outside of my knowledge.
I researched this quite a bit before buying but strangely enough didn't I see anything about hot-spotting. I didn't even know about it until I got my problem and looked into it.
The projector is places in the ceiling perpendicular to the screen. The mount might lower it about 30 cm from the ceiling (12 inches).
If I understand you correctly then you are saying that the projector was to close to the ALR screen and that's why I see the hotspot?
What can I then do in my situation? Will the other screen (FlexGrey) fix the problem (I'm unsure if that's also an ALR screen?).
The projector is in the back of the room so I can't move it back any more.
I talked to the shop where I bought both the projector and the screen, at the same time, about my room-situation and also exactly about that it would not cause a problem with the placing of the projector and the (almost) max zoom.
When I later returned to the shop with my issue they simply said it's a hot-spot issue and some people notice it and others don't so they did no error - which I believed so I started talking to the screen manufacturer instead.
I didn't buy the JVC because it was around 20% more expensive, if I remember correctly, and I didn't see the point.
Yes the hotspot is being caused because the projector is too close. In this case there's nothing you can do with an ALR screen of that size in that room.
The grey screen seems to be a matte surface:
I still don't know why you were recommended an ALR screen.
Usually ALR or grey screens are for untreated rooms, to help with room reflections or even some ambient light. However with that projector the room should be treated and a white screen used.
Here's what an untreated room does to black level/contrast:
While ALR screens are somewhat effective at fighting ambient light, the best way to deal with this is by treating the room. The area closest to the screen, ~5', would benefit the image the most. This includes the ceiling, screen wall, and floor (dark rug).
There's a thread on room treatment here:
Grey screens are much less effective at fighting ambient light than ALR screens.
There is another solution, that's paints with ALR properties. The paint mix can be customized and fitted to your setup so no hotspot. However the less artifacting (hotspots), the less light rejection properties the screen has. Paints can be applied on a cheap white screen or a smooth white wall.
There's an argument that a paint mix would be beneficial even in a treated room since the Sony is not the best when it comes to black levels.
There are some ALR screens which artifact less or very little at 1.5x throw ratio, but they are north of $4000, and the side rejection capability is not good.
All of this being said, you should not pick a screen until you've used the projector for a while on the wall. General ratios are general, but from what I assume a viewing distance of 350cm, an 118" screen is rather small.