Da Lite HP Screen Gain - AVS Forum
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post #1 of 16 Old 12-05-2012, 01:51 PM - Thread Starter
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I want to know how much gain will I get from my screen at 2in, and 8in above my head with a HP 2.4 screen. I'm at eye level now, but I'm rearranging for my two projector set up. At eye level its great, but sometimes I move my head and I'm in the light path. My JVC will be dead center and my Benq right above. I know at eye level I get full gain but o don't know the gain when its above my head
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post #2 of 16 Old 12-05-2012, 02:03 PM
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Quote:
Originally Posted by blee0120 View Post

I want to know how much gain will I get from my screen at 2in, and 8in above my head with a HP 2.4 screen. I'm at eye level now, but I'm rearranging for my two projector set up. At eye level its great, but sometimes I move my head and I'm in the light path. My JVC will be dead center and my Benq right above. I know at eye level I get full gain but o don't know the gain when its above my head[/quot

As long as you're asking I'd like to know what I'd get at 2' & 3' above me. Two different projectors, VSPro8100 & Epson 3010 for 3D.

Ed
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post #3 of 16 Old 12-05-2012, 02:26 PM
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crouch down in your seat till you are 8" below.. .. you will be fine!
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post #4 of 16 Old 12-05-2012, 02:26 PM
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Quote:
As long as you're asking I'd like to know what I'd get at 2' & 3' above me. Two different projectors, VSPro8100 & Epson 3010 for 3D.
Ed


Very little to none.
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post #5 of 16 Old 12-05-2012, 06:10 PM
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Originally Posted by airscapes View Post

Very little to none.

Really?

With the pj's lens about 2 feet above my head when seated I wouldn't experience a substantial increase in gain going from a 1.3 screen to a 2.4 HP? This is with a 18' throw and a Viewsonic Pro8100, also an Epson 3010 with a 13 1/2' throw.

Thanks!

Ed
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post #6 of 16 Old 12-05-2012, 07:42 PM
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2 or 3 ft.. 2 you would get some, 3 no.. That is the way it works..
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post #7 of 16 Old 12-06-2012, 06:12 AM
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Download the "High-Power Screen Gain Calc" in post 566 of the "Da-lite Hi Power New or Old what did you get?" thread. Enter your distances into the spreadsheet to determine the gain you'd get with different pj placements:

http://www.avsforum.com/t/1213577/da-lite-hi-power-new-or-old-what-did-you-get/560_40#post_19889242
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post #8 of 16 Old 12-06-2012, 01:05 PM
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Originally Posted by airscapes View Post

2 or 3 ft.. 2 you would get some, 3 no.. That is the way it works..

I could move the VS8100 to about 18" above eye level but couldn't get the Epson 3010 any closer than 2 1/2'. The Epson is plenty bright in 2D but it'd be nice to have it brighter in 3D. I guess you just saved me a bunch of $$$.

Ed
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post #9 of 16 Old 12-08-2012, 02:57 PM - Thread Starter
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Quote:
Originally Posted by henrich3 View Post

Download the "High-Power Screen Gain Calc" in post 566 of the "Da-lite Hi Power New or Old what did you get?" thread. Enter your distances into the spreadsheet to determine the gain you'd get with different pj placements:
http://www.avsforum.com/t/1213577/da-lite-hi-power-new-or-old-what-did-you-get/560_40#post_19889242
I wonder how accurate this calculator is, I assumed that I would be getting maximum brightness in my setup now, with it being at eye level. But raising the projector 8in above my head, I got 2.2 gain. Then at 14in above my head, the calculator says 2.0 gain. The gain can not be that high.
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post #10 of 16 Old 12-10-2012, 03:34 PM
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Quote:
Originally Posted by blee0120 View Post

I wonder how accurate this calculator is, I assumed that I would be getting maximum brightness in my setup now, with it being at eye level. But raising the projector 8in above my head, I got 2.2 gain. Then at 14in above my head, the calculator says 2.0 gain. The gain can not be that high.
What is your seating distance and PJ distance? at longer throw, the error angle becomes very small.

"A wide screen just makes a bad film twice as bad. "
-Samuel Goldwyn

I wonder what he'd think about 3D IMAX?
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post #11 of 16 Old 12-11-2012, 11:56 AM - Thread Starter
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Originally Posted by dougri View Post

What is your seating distance and PJ distance? at longer throw, the error angle becomes very small.
I'm 17.5 ft from a 120in HP 2.4. The projector is 18.5 ft away.
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post #12 of 16 Old 12-11-2012, 01:31 PM
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Quote:
Originally Posted by blee0120 View Post

I'm 17.5 ft from a 120in HP 2.4. The projector is 18.5 ft away.

look at the angles involved... assuming you are in line with the projector (no offset to right or left), and your eyes are at screen center vertically, the angle between your eyes and a direct return to the PJ is arctan(14/222) = 3.6 degrees. Of course, you are likely offset from center a foot or two, and the center of the screen is likely a bit above eye level, but 2.0 does not sound unreasonable at that seating/PJ distance... loss of lumens from the PJ at that throw is likely to be more of an issue though.

"A wide screen just makes a bad film twice as bad. "
-Samuel Goldwyn

I wonder what he'd think about 3D IMAX?
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post #13 of 16 Old 12-11-2012, 02:13 PM - Thread Starter
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Well, I'm going to have a chance to see how it look soon when my other projector comes. Hopefully it is close to 2.0 gain, that would be good
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post #14 of 16 Old 12-12-2012, 06:28 AM
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Quote:
Originally Posted by airscapes View Post

crouch down in your seat till you are 8" below.. .. you will be fine!

Quote:
Originally Posted by airscapes View Post

Very little to none.

You will still get a fair amount of gain. I use an old Marantz VP-12S4 mounted 2' above my head, shooting onto a 106" 2.8 gain HP screen. The Marantz is used in low lamp (250 lumens) and I get a very bright punchy image. If you go to the old High Power thread and do a search for the screen calculator, you can figure out exactly how much gain you would get.

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post #15 of 16 Old 12-12-2012, 07:20 AM
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Originally Posted by AV Science Sales 5 View Post

You will still get a fair amount of gain. I use an old Marantz VP-12S4 mounted 2' above my head, shooting onto a 106" 2.8 gain HP screen. The Marantz is used in low lamp (250 lumens) and I get a very bright punchy image. If you go to the old High Power thread and do a search for the screen calculator, you can figure out exactly how much gain you would get.

Yep the 2.8 rules, and if he was able to get one I would agree, but after having both the 2.8 and 2.4 next to each other, I can tell you they are markedly different. The 2.4 at eye level is about what I get form my 2.8 at 20" The off axis of the 2.4 is better than the 2.8 but you hit the bottom gain of 1 much faster than with the 2.8, at least that was what I saw when comparing them side by side with the same projector.. .. your mileage may vary..
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post #16 of 16 Old 12-16-2012, 12:51 PM
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I can only give you anecdotal evidence, but I just switched from a Carada Brilliant White 1.3 to a new High Power in a room with no light control and the difference is shocking. Projector is 3 feet above our head and I'm cannot believe how much brighter the projector is. I did not expect such a dramatic difference.
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