Originally Posted by Drew Dough
I really appreciate all your help.
I will keep digging and doing my research and read more of the links you shared.
Not to make you repeat yourself, but just so I can understand more clearly. If my room is completely dark, night time viewing with no lights on in the house, but light colored walls. Which is better for reducing the washout from the reflection of light off the walls? I originally thought ALR such as Cinegrey would be best for this since it reflects the light back towards the source (and not to the walls surround the screen). Are you saying I am not correct here? That a High Contrast screen like the ST would be better than a Cinegrey to avoid the washout from the light colored walls?
The ST HC grey has 0.67 gain. It does have ALR properties. The shade of grey looks around 0.6, which means for until 0.67 there is the ALR film.
The 3D claims a 1.2 gain. It's probably closer to 1.0. The shade of grey looks around 0.5, which means to achieve 1.0 it needs 0.5 gain in ALR film.
The ALR film is at least three times more reflective on the 3D than on the ST HG. Approximate values.
It's this film that will probably raise the black level. If a hotspot is present, it will raise the black level even more.
The ALR film is what gives the 3D it's light rejecting capabilities. The grey base lowers the brightness of the image.
The 3D claims 65% ambient light rejection.
Every time ambient light hits the ST HC, it will only reflect back 67%.
If you had two samples of fabric, one white and one grey, to reach the same brightness on the grey the brightness on the projector would need to be increased by the amount of negative gain the grey screen has.
With a grey screen the brightness level can be kept lower because:
But our eyes don't always pick up the white levels looking all that darker, though we may notice the lower black floor now.
The 3D might be better at fighting ambient light, but the same reflective film that helps it do that is also what will give raised blacks over the ST HG. The ST HG also have a small amount of ALR fighting capabilities.
There is no way to 100% eliminate hotspot, it's always there, even if it's not obvious.
At least this is what I think is happening.
Best to test it live with samples.