HIGH POWER a Review! Part 1 - Page 119

Originally Posted by millerwill

This new gray HP screen really is one of the more exciting things to happen wrt screens in quite a while.

Where are you, Tryg?

Originally Posted by Hughman

Why do you need Tryg, his viewing it won't change how it performs. Order a sample and see how it works for you.

Originally Posted by Hughman

Why do you need Tryg, his viewing it won't change how it performs. Order a sample and see how it works for you.

Originally Posted by Hughman

Think about the 2nd reflection then the third and fourth, a screen of less gain kills them quicker. Lets say we have one screen with a gain of .9 and another with a gain of .5 and we increase lumens to maintain equal screen brightness on the .5 gain screen, lets' see how each potentially kills off reflections bouncing around the room.

(.5 screen).... (.9 screen)
360 lumens.... 200 lumens

180...............180
90.................162
45.................146
22.5...............131

What exactly was everyone debating in that thread. Only on AVS could this be debated endlessly. The racquetball vs squash ball analogy is a decent representation, even if you drive a squash ball harder to equal the speed of a racquetball off the first wall, the ball will still die much quicker after that.

Originally Posted by millerwill

But if the white HP and gray HP both have gain 2.4, won't they both produce the same brightness (ftL) coming off the screen?

Originally Posted by R Harkness

Yes, essentially. But when erkq said a gray screen just "cuts everything equally" that implied he was talking about gray screens in general. And gray screens can help preserve contrast over a white screen.

Keep in mind that if both the Da Lite gray and white screen end up with the same gain, the gray screen is going to need more optical gain applied to make it as bright. Typically the more gain applied to a screen substrate the more likely you are to see it's effects in the picture - sparklies/specklies etc.

Though Da Lite seems to have come up with a very nice coating for their HP screen. Hopefully screen texture will remain subtle even if they have to put more on the gray screen.

Originally Posted by Tryg

I saw the post that they now have a gray screen. Lets see how the response goes then in the fall I'll probably contact da-lite to work something up. It's been five years...maybe it's time to whip something new up

Originally Posted by Drexler

Millerwill,

The HP doesn't hotspot due to its retroreflective nature. Though I imagine the new HC HP will have a real narrow viewing cone.

Regarding the use of a grey substrate. I'm trying to get my head around it, but as I see it it can't increase contrast, only lower the black level together with the white level. If shooting with the same projector on the same type of screen (the same directionality) but one with a white substrate and one with a grey - to me they would produce exactly the same contrast but the white one would be brighter.

Since brightness is a big asset in todays projector market (just read the JVC threads! - you pay BIG money for a high performance projector that also is bright), I don't really see what the grey substrate brings to the table? Well, unless you have a small screen...

Or am I missing something?

Originally Posted by millerwill

But I still having trouble getting my mind around the brightness and CR of the HC HP vs. the white HP. If they both have 2.4 gain, then they MUST give the same brightness (ftL) with the same pj; i.e., ftL = gain*lumens/(screen area), there's nothing in the eqn about whether the screen is white or gray. So it seems that the two screens would perform EXACTLY THE SAME except for the higher rejection of reflected light by the HC version because of its narrower viewing cone.

Originally Posted by millerwill


Another concern is that Dalite quotes the viewing angle as 20 deg for the HC HP and 30 deg for the white HP. I thought they quoted 30 deg for the old 2.8 HP, but am not sure. But is does seem that the new HC HP has an even narrower viewing cone.

Originally Posted by millerwill

And finally if the gains of the HC and white HP screens are the same, isn't their white level and black level the same? and thus their CR the same? The only difference would thus be in wall reflections, less for the HC because of its narrower viewing cone.

Originally Posted by R Harkness

Which is quite predictable. The way gain works is by focusing light toward the desired viewing position. The more gain you apply, the more focusing of the light, the narrower the viewing angle. So even if the gray and white screen ultimately have the same gain rating, the gray screen needed more focusing of the light to get it to the same rating. Hence, narrower viewing angle.

Yes. But since wall reflections can have effects on contrast, in a room with brighter walls the HC should do a better job preserving contrast.

Originally Posted by erkq

Did my discussion a few posts back (#3555) about how a lower gain screen effectively improves the contrast performance of the room make any sense?

Originally Posted by millerwill

The point is that the HCHP is NOT a lower gain screen than the white HP, at least according to Dalite's info (though we'll wait to hear from ones who see it); they are both listed as 2.4 gain. The only way I see that they could differ is how the HCHP reduces wall reflections because of its narrower viewing cone, as RichH pointed out.

Originally Posted by millerwill

But again, DarinP has noted that white walls do NOT effect o/f CR, because when the light is 'off' there are no reflections, and when it is 'on' (100% IRE) the reflections are swamped by the light from the screen. Refections thus effect only the effective ANSI CR.

Originally Posted by millerwill

The only way I see that they could differ is how the HCHP reduces wall reflections because of its narrower viewing cone, as RichH pointed out.

Originally Posted by millerwill

But again, DarinP has noted that white walls do NOT effect o/f CR, because when the light is 'off' there are no reflections, and when it is 'on' (100% IRE) the reflections are swamped by the light from the screen. Refections thus effect only the effective ANSI CR.

Originally Posted by millerwill

I know that the normal HP's don't hotspot (I have a 2.8HP), but was just wondering whether the higher reflective surface of the HCHP2.4 might. I hope you're right, that it doesn't.

Originally Posted by Drexler

The new HP won't hotspot. It's pure physics.

Angular reflective screens with gain have aluminum particles that works like tiny diffuse mirrors. They reflect incoming light at an angle that is equal but opposite the incoming light. I.e. light falling in at a 15 degree angle from above will be reflected downward with a 15 degree angle (see illustration). Light that is hitting the sides of the screen will have a higher angle of incidence and will be directed outwards towards the walls to a higher degree compared to light hitting the center of the screen which will mostly be reflected straight back to the viewer. Thus the center will be brighter and hotspotting happens. The further back you can put the projector the smaller the difference in angle of incidence between the center and sides of the screen and the less hotspotting you will see.


The HP however gets its gain from microscopic glass beads that collects incoming light and sends it back to the source. Light coming in at 15 degrees from above will be sent back 15 degrees upwards. And light hitting the far sides of the screen will be directed back towards the projector the same way that like light hitting the center of the screen - thus you get the same gain at the center and the sides and equal brightness all over the screen. No hotspotting.



So no matter how much beads they will add to the substrate to increase the gain and directionality it will not hotspot. Of this I'm sure.