Originally Posted by Dhiren Raghvani
Thanks, Im limited on how far back i can go, but if I am reading this right if I brought the PJ closer to the screen (10"7) I would be ok with the HT3550. Any further and the TK850 would be better? Taking into account this has nothing to do with PQ as per the info from bdht? Apologies for all, the questions, im learning on the job!
Why would placing the HT3550 closer be better? It would be worse.
ALR related artifacts to affect do affect PQ.
This kind of setup is more and more familiar, relatively small untreated rooms with/without ambient light, with small throw distance.
Short answer is a TV.
I haven't tried bdht's setup with a low gain (i.e. 0.25) screen and a solid state projector.
I don't believe there are any ALR screens that would have NO hotspot at short throw ratios. Some screens with less light rejecting properties may have a diminished hotspot, but at 1.5x or lower it's a risky proposition.
The higher the ambient light rejecting properties, the longer the required throw range.
Any ALR can have a hotspot. It's less to do with the quality of the fabric and even the gain and other characteristics, and more to do with the technology, of how angular ALR works.
The optical coating is used to increase the reflectivity and hence the brightness of the image, so it doesn't get too dim. The coating also makes the reflective characteristics of the gray screen more mirror-like in it's directionality, so that the projector light is reflected more towards the viewer, less on to the surrounding walls. (If you are facing a white wall and someone shines a fashlight from above your head on an angle at the wall, the white wall will diffuse the light and light will scatter everywhere, lighting up the rest of the room, like a white screen does. Replace the wall with a mirror - now there is no diffusion of the image of the flashlight - what you see reflected is the focused beam of light right into your eyes). In this way, gray screens with optical gain can have a satisfyingly bright image while also helping maintain good contrast if you have some ambient light, or reflective room surfaces.
BUT...there is a trade off. When you add optical coating to make the reflection more mirror-like, you are of necessity focusing the light to a smaller central area of the screen. This results in uneven screen illumination known as "hot-spotting," where - especially apparent if you have a blank white image - you can see the projector beam being focused more in the center of the screen, and the screen dims significantly as you move off center to the edges of the screen. So it's like a mild spot-light effect in terms of brightness.
If you want to see how the hotspot manifests itself in different lightning and type of picture scenarios. check this posts. In my posts, the hotspot on bright screen looks better IRL, but not by much. The camera can affect how the hotspot looks in pictures:
There may be a paint mix that you can paint on a budget screen, but I don't know if it will fare any better in high ambient light.
If you're willing to paint, maybe give that a try.
Originally Posted by bdht
In the future you can consider something like the Da-Lite Parallax .8, which wont be subject to hotspotting, has no gain artifacting, has a wide horizontal viewing angles, completely rejects light from above and below(which results in a low vertical viewing angle but not an issue if eye height is at 1/3 image height or higher). Or wait for actual black materials or paint a budget screen a 0.25gain black and use a brighter solid state projector.
What about a projector with high color lumens like the HC1060 and a 0.25 gain screen?
I haven't tested other ALR's personally, but from the specifications I don't see how the Parallax 0.8 will not have any artifacts.
Parallax Pure 0.8 claims a 0.8 gain, 85 degree horizontal half gain, 17 degrees vertical half gain, and a recommended 1.5x (or higher) throw.
The specifications look very similar to the XY BC 0.8, with maybe the exception of the vertical half gain.
The dnp Supernova 08-85 is identical in specifications:
The EVP DarkStar 9:
0.9 gain, minimum throw 1.5x, 180 degree viewing angle.
Have you tried these ones?
0.9 gain, 1.3x minimum throw, 75 degree half gain.
Elunevision Aurora ALR:
1.3 gain, 1.2x minimum throw, 61 degrees half gain.