Has anyone tried a dark gray (off black?) border? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 6 Old 06-21-08, 07:25 PM
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Has anyone tried a dark gray (off black?) border?

After looking at a lot of screen shots and my own screen, I've been wondering if a dark gray border might work better than a nearly black one. It seems to me that the border is supposed to be your "black reference" and if it is blacker than anything on your screen, your brain will say that your screen blacks are not black.

To test this I played around with some of the BW test shots using Windows Paint. What seemed to work best was to select the darkest black in the picture and use that for the border. Since this was often brighter than the background walls, I added a second lighter gray border around this. The results were pretty interesting, even the blacks that looked bad in the test shot suddenly looked really black. By the same token, if you make the border "absolute" black, everything looks not so black (even the shots that previously looked very black).

I'm not really surprised by this, the brain is a fantastic image processor and is always "correcting" what it sees. You seldom see anything in perfect lighting (whatever that is). So while it makes sense to get the projected image as close to "real" as possible, it also makes sense to let your brain do its thing by making the cues correct.

The only problem is how to implement such a border. One idea I had was to back light a white translucent plastic border which is partially painted translucent gray to create the border. By adjusting the light level very low, you could get the gray part to just the right level to match your blackest blacks and the remaining white border (actually now just a lighter gray) would fool your brain into taking the dark gray for "black". I'm not sure how I would do the back lighting, but rope lights or LED's come to mind. I do not think you could use any kind of front lighting since it would be difficult if not impossible to keep it from spilling onto the screen. But perhaps if the screen is offset from the wall there could be some way to back light the "black" border and the background wall with lights under the screen. My concern is to somehow get the border lighting very even and I think bulbs too close to the border would not work well.

But before I spend too much time on this, I was wondering if anyone had tried something like this or if anyone has some better ideas to implement this.

Last edited by al_mo; 06-21-08 at 07:32 PM. Reason: Correct title spelling
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post #2 of 6 Old 06-21-08, 08:46 PM
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Re: Has anyone tried a dark gray (off black?) border?


Interesting concept. The thing to remember though is that the black velvet border also absorbs some overspill by the pj. If you go with something gray, you need to be perfect in your design/build.

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post #3 of 6 Old 06-22-08, 01:09 AM
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Re: Has anyone tried a dark gray (off black?) border?

What mech said, he beat me to it!

As far as borders and wall colors, you are absolutely right. If you have a darker wall the whole image will seem like the blacks are darker, and also the whites on the screen will look better too! The border though is more than just a black reference, it also serves the purpose of soaking up any image spill from the projector. If you can get a perfect border and the image is completely within the border, then this isn't an issue.

Some materials work much better at absorbing the spill light better than others. With my old projector I was perfect within my border except the top and bottom (I had a 4:3 projector but went ahead with a 16:9 screen anyway since the PJ had a 'wide screen' mode) Now that I got a new projector, and one that is brighter than the old projector, it does have some spill on the border.

Originally I used Black Suede and it worked great as a border. I used it for a couple of reasons:
  1. I was testing screens and ended up with something that looked really good and I needed a border to fully present it.
  2. The store didn't have black velvet, but recommended black suede. At first I balked at the idea, but it looked nice and at $2.50 a yard I thought it was something that should be checked out.

For the price it really does work extremely well, but it does not absorb spill light anywhere near what black velvet does.

If you are perfectly within your border, then sure you can play with some creative borders. Another thing you can do is to make a very thin black border, something along the lines of an inch wide, and then put trim up around that so you have an inner black border and then a decorative outer border. It's more work, but would look nice as well as still give you that spill area as well as a black reference.

I found that a black border really does pump up the perceived black levels in the projected image. It's not that the border is black so it makes everything else 'not look black'... everything else really isn't black to begin with. What it does is it 'tricks' our eyes into seeing the black border and our eyes and brain then equate everything to 'black'- well, everthing in the projected image that is supposed to be black! It's the same as how a gray screen can produce amazing whites, that is until you throw a white reference up on the screen for your eyes and brain to then use as a reference comparison. Now those whites don't look white... remove that white reference and you get your whites back. Same concept with the black border.

"Make everything as simple as possible, but no simpler." - Albert Einstein

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post #4 of 6 Old 06-22-08, 09:42 AM
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Re: Has anyone tried a dark gray (off black?) border?

Thanks guys. I've got 3 yds (x60") of black velvet which I was planning on using. At $10/yd it's not cheap, but it will allow me to get 96+" lengths with no seam. And I can use what's left over for masking if I think that's needed. The side walls and ceiling around the screen will be covered with some black burlap-like 2'x4' panels for about 4 ft. I had them up before I decided to paint the rest of the room dark and they worked great. The place I work at was scrapping the panels which were part of a "portable" exposition booth. They are really nice, almost as black as velvet with very little reflection. By placing them away from the walls and ceiling, they double as an acoustic damper. My wife said it looks like a display at an AV store (I have to admit it turned out much better than I thought it would).

My PJ (HD70) has little spillage that I can detect. The little I can see is at the same level as the "blacks" from the DLP, so I guess it could be used to illuminate the border, which would then need to be the same color as the screen . Any other ambient light would just do the same thing (make the border and the blacks the same color). Surrounding the border with a lighter illuminated border would complete the trick (which sounds like the old halolight concept). At first blush this seems like it would not work, but I've seen stranger things.

One of the things that got me thinking about the border happened a long time ago (late 1970's). I built my own PC (before the days of commercial PC's) and had designed and built a video card for it. At the time I was working with commercial graphics displays at work and really liked the idea of a light pen (this was before the mouse became popular). So I designed a light pen into my graphics card. It simply detected the passing of the CRT beam as it lit up the display and could thus capture the location on the screen. Anyway I had a problem that it worked fine on the left side of the screen but not on the right. After putting an oscilloscope on it I determined the cause: the blacks on the left side were as bright as the whites on the left side. But the funny thing was that nobody looking at the screen would say that was true. The monitor was an old B&W with terrible voltage regulation and I fixed the problem by beefing up its power supply. Ever since then I've been really aware of what your brain can do to any picture. Artists have always taken this into account (I've dabbled in painting, but never had the time to get any good at it).
post #5 of 6 Old 06-22-08, 10:20 AM
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Re: Has anyone tried a dark gray (off black?) border?

Bill and mech are taking care of you, but I did want to say WELCOME to the Shack, Al!
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post #6 of 6 Old 06-22-08, 10:38 AM
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Re: Has anyone tried a dark gray (off black?) border?

Thanks Jim, those guys really are helpful.

Looking at some of the latest BW posts, the shots with lots of light where the BW paint extends beyond the image to create a ragged border seems to show what I was thinking -- I haven't tried it, but I'll bet if you change that "border" to true black, the screen would look more washed out.


black , border , dark , gray

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