Is there a practical method of lowering gain on existing projector screen? - AVS Forum
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post #1 of 8 Old 12-14-2012, 10:36 AM - Thread Starter
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Has anyone tried or knows method to lower gain on existing projection screen (pull down)? I installed screen with 1.0 gain and it needs adjustment cause it reflects too much light back to my white ceiling which bounces back later brightening the picture. I performed several tests with test pictures and it is obvious that I need a lower gain screen. I hate to replace screen because it cost time and money. I thought about something like spray paint that I could apply onto existing screen without risking of getting it stuck. Has anyone tried something like that or similar? Any suggestions and ideas are appreciated.
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post #2 of 8 Old 12-14-2012, 11:15 AM
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You can get a ND (neutral Density) filter for the projector (search the projector forum) but the best way to fix this is to treat the walls ceiling and floor. There are many methods paint, fabric (triple black velvet is the best light absorber) you can make removable panels if there is some wife or rental issues that prevents you from making the changes permanent. Here is another tread addressing the issue from a different forum. http://www.avsforum.com/t/1442134/do-dark-walls-matter-yes-yes-they-do/0_100
Unfortunate fixing the issue is the best way to go.
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post #3 of 8 Old 12-15-2012, 06:26 PM
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Actually you might be better off with a higher gain screen which has less scatter of the reflected light.

Angular or retroreflective depends on pj and viewer locations.

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post #4 of 8 Old 12-16-2012, 08:05 PM - Thread Starter
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The reason I ask was a flaring presence when playing movies with my new Optoma HD23 projector. I heard some users complaining that this projector might be too bright for rooms other than typical man cave with dark walls. I wanted to dim flaring by using low gain screen (0.8) which would also reduce amount of reflected light from the screen that would bounce off the walls back to the screen. Using high gain screen in my case would be a mistake if Optoma is just too bright for my environment.

So I made an experiment today running my old Infocus projector (750 lumens / 1:2000 contrast comparing to Optoma 2500 lumens / 1:5000) on same screen same room and found flaring is gone with picture becoming darker but more color vibrant and natural looking without washout. This made me thinking that my new Optoma HD23 is indeed too bright for typical 500 sq.ft. living room with beige walls and drapers, while ceiling and dark floor (I watch in complete darkness). I used same screen and result was stunning. The old projector (with replaced 117 hrs only lamp) far much dimmer creates black level I desire, while my new Optoma not only lights up dark scenes filling black areas with “grey” that cannot be controlled. Of course my old Infocus is a history so I look forward to test dimmer Hd33 tomorrow.

One other thing that I wonder is the projector position. Currently I have no option to mount it on the ceiling and Optoma sits on the stand leveld with bottom edge of the projeciton screen so the light angle is directed up which makes me believe that I am getting increased amount of light reflected off the screen toward my white ceiling comparing to projector mounted under the ceiling where light beam is directed on bottom angle. One way or the other I am positive about my Projecta screen I have which is absolutely uniformed, and allows me to watch movie form any angle including super sharp angles, it is pretty amazing actually. Still, subject problem remains unresolved. Hopefully this will change tomorrow.
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post #5 of 8 Old 12-17-2012, 04:20 AM
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Properly calibrating your projector or having a pro do it will increase the color accuracy and reduce the light output. Make sure you are using the cinema/movie preset, have uses a calibrations disk to properly set the brightness and contrast, and if the projector is still to bright look into an ND filter to lower the light output, they are very inexpensive ($20+-). This filter is like putting sun glasses on the lens .. cuts light but does not mess up colors.
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post #6 of 8 Old 12-18-2012, 03:19 AM - Thread Starter
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Got HD33 yesterday and found working ok wih no flaring presence. It is much bigger projector and somehow slightly more noisy but does the job. Looks like HD23 is going back to the store. It is great projector for the buck but for dark rooms with picture diagonal size of 150" or more. Not for typical family rooms like mine. Problem seems to be solved.
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post #7 of 8 Old 01-01-2013, 12:45 AM
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A neural density filter for the projector is a great idea. You could get several for less than the cost of paint. You'd also have the additional advantage of stepping down the amount of light reduction by changing filters as the projector bulb ages and dims. It's relatively easy to cut light back on a projector, a lot tougher to create more output from a given projector.
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post #8 of 8 Old 01-01-2013, 05:55 AM - Thread Starter
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True. I actually got and tried hoya nd2 filter with my my hd33 and found picture improvement in lamp bright mode. Colors in scenes with wide brightness dynamic range are not washed out anymore and blacks are slightly better. In lamp standard mode or in 3D the picture becomes too dark so filter has to be removed.
The trouble is that with lack of thread on Optoma focus ring doing it is not very comfortable.

After couple of weeks with Optoma hd23 and hd33 and the issues with both models like distorted picture geometry due to flaw in hd33 lens projector or lack of Puremotion in hd23 I have decided to upgrade to hd8300. Hopefully this model will solve all my problems with much better lens and best iris in class - as I heard.
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