Blend zone in dark scenes

How to optimize games for NTHUSIM products.

Postby tezzzaaa » Tue May 24, 2016 6:56 am

hi everyone. New to these forums and new to projectors but I'm a long time multi monitor user..
I'm running two projectors (optoma hd141) side by side on a flat screen for gaming and movies and I'm using Nthusim+ for edge blending
It took me a while but I now have a seamless blend and perfectly matched colors and it looks stunning.
However the only issue I have is being able to see the blend zone during dark scenes. Is this usual?
I'm aware the mouse wheel adjusts the amount of shading used but no settings cures it
It's not a Hugh problem to be honest but it's the only thing stopping it from being 100% perfect. Are there any tricks to solve this?
The only thing I've found is that ambient light seems to make it fade but also decreases pic quality.
I have searched the forums but can't find any mention of it.

Thanks in advance

P.s. My specs in case it matters

Win 8.1
Amd 9370
2x980 sli
12 gig ram
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Postby BHawthorne » Tue May 24, 2016 5:07 pm

There are a couple of things that can lessen the issue.

One is the gamma setting of the projectors and in the video driver. You might experiment with the gamma settings a bit to see if that lessens the issues. Gamma settings really effect the blend profiles a lot depending upon what the gain is for the screen material you use and the gamma setting in both the projectors and the video driver.

With 100% black, you get that overlap area on the blend where the projectors are still doubling up on light. Even when a projector projects black, it's not a true black. There is still some light being projected. At issue is in that overlap. A method I use to lessen both hard edges on the overlap is to apply a bit of black electrical tape directly onto both projector lenses right at that very edge of the projected light. This diffuses that edge so it's not a hard break on the edge of the projection. Instead it ramps into a diffuse drop off. It seems to do the trick on my personal setup. You might still have a bit of a hot spot in the middle of the blend but on the edges there'll be no longer an issue. If the blend ramp isn't right after apply the tape you might move the tape around a bit to better align it to the very edge of the projection on the lens. It takes me 3 or 4 adjustments before I got mine to properly diffuse where I wanted it to.

Hopefully these two tricks will help get things looking much better in the blend areas.

-Brad
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Postby tezzzaaa » Sat May 28, 2016 7:22 am

Hi Brad.
First off thank you for the reply and suggestions, it's clear from these forums your very dedicated to Nthusim and helping it's customers. It's very commendable.

I've been playing around with your ideas for the past few days.
I had tried gamma settings on the projectors before but not the gpu drivers. Doing so does make a small difference but I find that by the time I've made it bright enough to make a difference in very dark scenes the picture quality is terrible and the colors look washed out.

As for the tape method, do you stick your tape to the lens directly? Also what projectors do you use? With the optoma the lens is sunk into the projector in a sort of cave making it very difficult to apply small pieces of tape. When I did this I found it always made a noticeable black smudge in the blend zone and also left a residue on the lens that was difficult to remove. Also the lens rotates when focusing so it was difficult to get the tape level vertically whilst keeping the projector in focus.
Another thing I did try is to put a bigger piece of tape on the rim of the cave so it's about 1 inch in front of the lens. Doing this I could make dark scenes look absolutely perfect but brighter scenes have a rainbow like effect in the blend zone. On a triple screen setup this wouldn't bother me but on a dual screen, the seem is right where the action is.

Any further thoughts or suggestions would be greatly appreciated.
I would also quite like to hear from some other members on this topic as I can't be the only one it bothers yet I find very little mention of it elsewhere.

Thanks
Tezza
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Postby BHawthorne » Sat May 28, 2016 1:50 pm

The gamma settings are highly dependent upon the gain of the screen. Some screens it'll matter more than others. We've had a few customers that have had the screen gain effect the blend profiles so much that they were outside the options available. We had them adjust their gamma to bring the profile options back into usable range. I'm not thinking that your issue is gamma/gain though. I think it's the hard break on the blend overlap where the projection brightness doubles.

The tape is not an ideal solution for many of the reasons you mention. I also think that depending upon your source for electrical tape that the adhesives are a bit different. Some more problematic than others. On a typical setup there is 12-15% blend overlap of the projections. Of that, I'm diffusing about 10% of that area. Just the very outer most edge of the overlap area. The hard part is making sure that the tape diffuses at the same angle as the edge of the projection and doesn't get too far into the overlap where it starts effecting the profile ramp. This isn't really something that is any of the tutorial content. It's just something I do on my personal setup to lessen the hard-break in the overlap. There are probably better methods to achieve a similar result that doesn't involve applying tape to the lens. This is an experiment on my part that turned out to work well enough for me that I just kept on doing it in the last few screens I've done. In my particular setup I use GT1080 projectors.
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Postby tezzzaaa » Tue Jun 07, 2016 7:18 am

Hey Brad.
Just thought I'd come back and say I've been playing around and now I'm pretty happy with the results. A mixture of the tape method, slightly turning up gamma on the gpu drivers and turning down brightness a tad on the projectors means I now only see the blend zone on 100% black screen and see a rainbow like effect only during very bright moments.
So thanks for your suggestions. I ended up using all of them so it was good advice. I will up some pictures when I get the chance.
Thanks again
Tez
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Postby BHawthorne » Tue Jun 07, 2016 3:41 pm

Looking forward to pictures. I always like to see new builds. It helps give me new ideas because everyone builds their screens just a bit different. :)

-Brad
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