Is it possible to use a projector outside of its focus range (over 300")? - AVS Forum
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post #1 of 10 Old 01-29-2014, 08:43 AM - Thread Starter
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I am making plans for an outdoor theater right now and am trying to come up with the best screen/projector combo to suit my needs. I am planning on using CarlofET's 10' x 24' flex white screen with a gain of 1.1. The issue is that the projector I am hoping to use, an Optima EH501 has a max focus distance of 30' and I need to place it at 33' in order to fill the screen.

What I am curious about is if it is possible to use a projector outside its max focus distance. In the past, I always assumed that the max focus on projectors was sort of like an "infinity" setting and the real limitation is brightness. If I were using a short throw lens, I could understand having a problem with going back too far, but I have seen many people use projectors outside the focal range on large outdoor setups. I am curious if this forces the image out of focus or if its not noticeable or maybe you can go a little bit farther but not much. Just wanting some input here, thats all.

I know that this forum places very high emphasis on video quality, and as a fellow enthusiast, I do appreciate the passion, but for this case, that really isn't the goal, I know the PJ in question is not designed for theater use and may exhibit rainbows with its 6x color wheel and the brightness won't be ideal. By my numbers, the projector should have a theoretical brightness of around 23fl, however, on videos, after a couple hundred hours, the actual brightness will likely be somewhere around 6-8fl. I know this isn't the target range for theaters but considering the setting of the theater, in the middle of woods on a farm, there won't be much ambient light, as it stays fairly dark even midday.
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post #2 of 10 Old 02-03-2014, 10:06 AM - Thread Starter
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No bites huh?
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post #3 of 10 Old 02-13-2014, 06:24 PM
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I use mine farther back than I should but I also run HDMI cables to get the best quality. It never gives me a problem. Try backyard theater forums. You may get a better or frequent replies.
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post #4 of 10 Old 02-16-2014, 02:33 PM
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For any given lens setting, the image will be in focus at exactly one distance. So, the distance you want to project is outside of the focusing range, the image will be out of focus. The further off you are in either direction, the worse the image will be.
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post #5 of 10 Old 02-22-2014, 12:27 PM
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Why don't you try it out first and then report back to us? I'd suggest using the side of an abandoned (or not) big box store in an empty parking lot. Portable power can be provided by one of those UPS backup things long enough for you to figure out what's up. I think it'll work FWIW. Enjoy.
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post #6 of 10 Old 02-27-2014, 07:34 AM - Thread Starter
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A quick update, I wound up getting an Infocus IN3128HD instead of the Optoma, the deal was just too good to pass up. First of all, the IN3128HD has a max focus that natively will support a 300" WIDE image, all of the other projectors only support a 300" DIAGONAL image, this was key because my image is going to be 290" wide, just inside the specs.

After it arrived, I started testing different settings, what I found is that it can focus perfectly as far away as I want it to, I wasn't about to try outside due to it being -10F right now but I tried it at the longest throw I can in my house, 48' (nearly 500" diagonal!) and I hadn't even maxxed the focus ring, it could still rotate further.

What is also interesting is that on the other side, I could focus the image MUCH smaller than the specs indicated, according to the specs, the smallest image I can get is about 40" diag, in reality, I was about to keep moving it forward and on the nearest focus setting, it was down to about an 11" diag image, MUCH smaller.

I find all this very interesting since I am used to manufacturers fudging specs in their favor, you would think that if they were going to go to the trouble of specifying focus distances and image sizes, they would at least state what their products can do, not far less.
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post #7 of 10 Old 02-27-2014, 07:39 AM
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You aren't going over the limit much so probably nth is going to happen, I use mine further as well and works fine

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post #8 of 10 Old 02-27-2014, 11:51 AM - Thread Starter
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Not going much over the limit? The focus limit is supposedly 32.8', I went to 48', and it had more room to rotate, that is at least 1.5x the limit. On the flip side, they say that minimum is 3.94', I can go to 1.25', or about 1/3 the minimum focus, I would say that is a pretty big disparity!

I am going to try it outside on the side of my house when it warms up, I am curious if the focus really is an infinite thing.
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post #9 of 10 Old 04-05-2014, 12:19 PM
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I didn't know anyone listed maximum focus lengths, usually you just get minimum focus and then a max size roughly based on lumen output. Unless you end up with a rare case where the focus wheel has a very small limit, most PJs can focus out ridiculously far. That last little bit of focus seems to stretch exponentially AND running out of focus on the far end is also very forgiving compared to running out up close.

This is one of only two complaints I have about my LG PJ, the focus ends at around 12-13'..way too short. Every other PJ I've ever tried feels like it could focus on the moon.

Simple <$250 dedicated black-fabric theater room, build in a day, takedown in an hour.
Easy $25-40 DIY black/dark-grey ambient-light rejecting screen, grab two things from a local store..mix..roll..done.
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post #10 of 10 Old 05-10-2014, 02:09 AM
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Your fine unless someone breaks infinity.

If your buying a new projector, buy more lumens than you will use. Running it in "Eco Mode" makes your bulb last 20-40% longer and reduces noise and heat.
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