A slightly positive gain fixed frame screen would make a fair bit of sense. It would possibly make more sense to use a light rejecting screen from a company like Draper (I believe they just came out with some new surfaces for this).
The issue as I see it is that if that's a true photo of the space, then there is a lot of ambient light which is falling right on the screens with no attempt to control that light which is near the screen.
Your current projectors are 4:3 aspect ratio, which is fine, if this was the year 1999, but computers have abandoned the 4:3 aspect ratio, as have televisions in general, so the recommendation by anyone who knows anything would be for a 16:9 or a 16:10 setup with maximum light output.
135" 16:9 screen is 54 square feet, asking for a projector which rates no less than 4,400 lumens. But, because of the serious uncontrolled ambient light, it seems like there is a need for as much brightness as you can afford, perhaps 100-120 lumens per square foot, or a 6,000+ lumen projector.
This is the list I would be pulling from as my recommendation at under $5,000 per projector:http://www.projectorcentral.com/projectors.cfm?g=1&hide=0&st=1&mfg=&p=500&p=5000&w=&r=&br=6000&br=60000&ll=<g=&t=&db=&dt=&c=&ar=Wide+%2816%3A9-10%29&dvi=&wr=&pjl=&pjw=&pjh=&td=&i=d&is=&sort=pop&sz=15
But, I would actually recommend more. Especially if there is a way to get the projectors out of the line of site of the congregation.
From this list:http://www.projectorcentral.com/projectors.cfm?g=1&hide=0&st=1&mfg=&p=5000&p=12000&w=&r=&br=6000&br=60000&ll=<g=&t=&db=&dt=&c=&ar=Wide+%2816%3A9-10%29&dvi=&wr=&ol=1&pjl=&pjw=&pjh=&td=&i=d&is=&sort=brt&sz=15
Something more like this model:http://www.projectorcentral.com/Epson-PowerLite_Pro_Z8350WNL.htm
with a long throw lens so the projectors can sit towards the back of the space instead of up near the front.
With their long throw lens, the projector could be as far back as 87' lens to screen.http://www.projectorcentral.com/Epson-PowerLite_Pro_Z8350WNL-projection-calculator-pro.htm
I would also recommend discussing with an electrician pulling any lights which are shining on the wall which the screen are on off the main circuit and putting them on a separate dimmable circuit if they aren't already. Get light OFF the screen, and that will significantly improve the image quality which is on the screen.
I'm not sure of any budget here, but the Epson would be my recommendation. I will actually be in a church later this week and will let you know what they went with at that location.
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