Originally Posted by ALRLIFE
I have a basement with black walls and a loft with white walls. I also had a Epson 6050 and JVC RS540. The 540's blacks on my alr screen with white walls in the loft was every bit as good as the plain boring white screen in the basement with black walls.
I believe people theorize on a bunch of diffent scenarios here without having any first hand experience with seeing various equipment in person. And a high end alr screen such as my Parallax and EPV Darkstar alr screens show ISF certified beautiful image quality with no discernible visual artifacts.
At what throw ratio? Black walls, does that mean dark paint or fabric? Have you used both the Epson and JVC in both setups?
Which screen do you have, the Parallax or EVP darkstar?
Those are high quality screens and don't cost 5-10 times as much as the 3D/5D for nothing. There are people that do find faults with even the best ALR's. Not the regular consumer I imagine.
The difference between different setups depends on variables, projector, throw range, lamp used, settings, calibration, type of screen, room environment, personal perception.
While I haven't personally tested, I assume that the JVC would provide better blacks in a black velvet covered room than a room with white walls and an ALR screen.
Are you saying my comments regarding the differences between these two setups are inaccurate?
n a room with white walls the pupil will contract making the blacks blacker, but loosing shadow detail. Even if the screen has a positive gain, more brightness is required to compensate for the reduction of light coming through the iris due to the white walls.
In a batcave the eye's iris will expand allowing for less light output from the projector since the image will appear brighter. With a velvet covered room the reduced light output reduces cross reflections. Reducing the light output can be done via closing the projector's iris, which also improves contrast.
The conversation started when discussing a JVC paired with a Cinegrey 3D, at 1.71x throw placed round the same height as the center of the screen, which I don't know how the 3D or other angular would react to it with respect to hotspot. Would probably get brighter.
Do ALR screens raise black level question is restrictive and requires a more detailed response.
With my 3D I get a massive hotspot at 1.5x throw (Benq HT3050). The hotspot does not diminish when changing the lamp to Eco.
As it's seen in the links with the white paper where the hotspot is (center), the screen is brighter than the paper.
The only time the screen is darker than the paper (in the center) (besides lights on), is when there is some part of the image that is bright. Then if there are large black block (like top and bottom bars) they are lighter on the paper.
This is probably because the ALR fabric is better at rejecting ambient light in proximity than the white paper.
All the screenshots:
From the front with a black image the paper is darker, but moving to the side the screen becomes darker, because of the half gain of the 3D (45 degrees).
The screen claims 1.2 gain, but a measurement of the 5D which claims 1.5 gain , resulted in a 1.0 gain rating. But honestly I don't know if I can believe the manufacturer's claim or the test.
The projector has a empty space between the lens and the casing. Covering this space reduced the hotspot (with a black image projected) visibly. I did not notice this change on a white matte screen.
This suggests the ALR fabric is raising the black level even when the projected image is a black image.
In the dark (projector off), the screen glows more than the white walls around it.
A recent setup with a 3D and a HC3800 resulted in a hotspot (white background) at ~1.7x throw. The JVC is less bright, but I don't know if that will eliminate the hotspot.
Another way to look at the hotspot is that is the actual brightness/black level of the screen, and the edges are darker because the projector is too close/bright.
However, I suspect that the reflective nature of (some) ALR screens raises the black level in comparison to a grey screen of the same shade, or even a 1.0 white screen.
The other factor that can raise the black level is the cross reflections from the white walls, which the screen can't negate 100%.
I previously had a matte grey Cinegrey the manufacturer claimed to be 1.0. It does not claim any ALR properites, so it can't be 1.0. Looks like 0.7-0.9 The blacks were significantly deeper than the 3D.
If the 3D is 0.8 as the measurement of the 5D suggests, how can it with it's 0.8 gain, darker shade of grey (than the Cinegrey matte) and ALR properties produce worse blacks than a matte grey screen?
If it's a positive gain, the shade of blacks and the ALR film should still produce darker blacks. Unless it's the ALR film that is raising the blacks.
In this review (https://www.passionhomecinema.fr/blo...is-de-gregory/
) the ALR fabric was used with projectors with throw ranges between 1.5-1.65x. It does not say in the review the ratio.
The manufacturer claims a gain of 1.5, the reviewer determined it's 1.2.
Reviewer did not observe a hotspot.
It was compared to a Lusoscreen Darkstar Flat with a 0.8 claimed gain. The shade looks darker though, maybe 0.6: https://www.lusoscreen.com/images/flat2_640.jpg
The room appears to have light colored walls with a regular height ceiling.
The reviewer claims the Lusoscreen is darker with better blacks. He also claims that the blacks are not affected by the 20% gain of the ALR.
Since the two fabrics are a similar shade of grey, how can the ALR produce worse blacks than the Lusoscreen? Shouldn't the ALR film actually help with cross reflections in the room, reducing the wash out?
If the ALR film that produces the gain really doesn't raise the blacks, then the ALR screen should produce better blacks than the Lusoscreen.
Generally speaking the ALR properties of a screen should be superior to a simple negative gain grey screen in reducing the negative effects of cross reflections.