Formula for minimum viewing distance for passive LCD? - AVS Forum
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post #1 of 7 Old 10-20-2012, 08:28 AM - Thread Starter
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Currently, I have 3D only on my computer, a 22" passive. I quickly noticed that if I sit "too close" (read: normal PC-using distance, about 30"), there's some crosstalk along the top and bottom of the screen. I know exactly what causes it, it's the slight gap between the LCD panel and the FPR layer above it, so that, because of the viewing angle of my eyes versus the top and bottom of the screen, the FPR is not aligned properly with the pixels underneath it.

It doesn't bother me so much when I'm gaming, because of how high I put the separation, so it doesn't look like a double-image. 2.35:1 movies don't bother me, because the crosstalk area is outside the visible movie area. 1.78/1.85:1 movies are a bit of a pain because of it, though. But, if I just sit back about another two feet, it all blends together very nicely (and actually helps the 3D effect a bit).

Anyway, I want to get passive 3D for the living room, too, and I'm also in the market to buy a house in the next six months or so, hopefully with a dedicated home theater room (probably made out of an extra bedroom). So I'm thinking big screen, maybe 60"+, but I don't know what the viewing distance will be.

Is there a way to figure out, based on the physical size of the screen, what the "minimum safe distance" would be to view full-screen (1.78:1) content with zero crosstalk? Does anyone know what the separation is between the LCD layer and the FPR layer? I'm assuming that's more or less a constant, that even with a larger screen, the two layers would be around the same distance from each other, rather than scaling with screen size (which seems silly). I'm thinking it's more a matter of the angle between your eyes and the screen, adjusted for the FPR layer distance.. I'm thinking anything more than about five or six feet would, in theory, be okay.

Any thoughts?

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post #2 of 7 Old 10-20-2012, 11:06 AM
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Yeah, I went through much the same process when I decided to get a 65" LG passive TV. I needed to have some idea of optimal viewing distance, so I could lay out my home theater accordingly (had to remodel a spare room). I read a lot of articles on the subject.

I don't have any links for you, sorry. No doubt you'll get some more replies and some links. But I personally settled on 1.5x screen size and it's been satisfactory...for me. That's round about 8 feet from my 65 incher. Any closer and the 3D degrades, any further and you lose immersion. Others will be sure to disagree, but there you are.
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post #3 of 7 Old 10-21-2012, 07:54 AM - Thread Starter
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Can you try this for me? (If you don't mind)

Can you tell me at what distance the crosstalk starts to creep in at the top and bottom of the screen? Like if you put yourself at the optimal center point for 3D, and then moved closer to the screen.. about how far out does the crosstalk start to appear?

As long as I can plan for a room with a greater viewing distance than that, I should be good.

Thanks!

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post #4 of 7 Old 10-21-2012, 09:32 AM
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Okay, I put in Hugo 3D (no pop-out gags).

At 8 feet, and assuming the screen is perfectly perpendicular, I can raise my head a little above or below the top/bottom edges of the screen before detecting any crosstalk at the further edge. Approaching the screen with my eyes at the level of the screen's center, I can approach as close as ~ 3feet before seeing crosstalk at the top or bottom edges. Actually, my TV is wall-mounted a little above eye level and tilted down enough to have my eyes perpendicular to center screen at seated position. But I did the best I could. It helps that my screen is very glossy and I could see my reflection if I opened the blinds.tongue.gif

Well before 3 feet, the 3D becomes uncomfortable to me. It's there, but fatiguing; progressively harder to focus on. Without watching for an extended period at various distances, I'd guess 6 feet would be my limit without getting a headache. YMMV.

I guess you could call that best case scenario for 3D, crosstalk aside. Let me give you a worst case scenario:

I capture 3D from cable with my Hauppauge HD-PVR over component. It's the only way I can watch them actually, because strictly speaking you need an HDMI connection for that, to manually put your TV in the proper mode. My HD cable box has component, no HDMI. Which is as I want it, because my HD-PVR would then be useless without component. Yes, we're talking SbS 1080i, which is less than ideal on a passive set. Still looks pretty good.

There's one capture I have, 3D Sun, which has very aggressive 3D, lots of pop out gags. That one is very fatiguing to watch even at 8 feet. At times, it takes some seconds to adjust one's eyes and see the 3D. In the interval, there's double-vision, like one took off the glasses.

In between you have 3Ds with moderate pop out. Off the top of my head, and this might not be the best example, there's Imax Space Station. It has a few scenes with fairly aggressive pop out. My eyes can handle those okay at 8 feet.

All that aside, and I'm sure you know this anyway, but you need a balance between immersion and 3D. They're not mutually exclusive, but 3D effect will tend to be better further out than immersion, for which closer is better, up to a point.

Since no one else replied yet as I'm typing this, here are a couple representative links, which I probably read when I was going through this process of figuring out proper viewing distance:

http://www.best-3dtvs.com/guides/best-screen-size-viewing-distance/

http://www.practical-home-theater-guide.com/3d-tv-viewing-distance.html

I hope that helped you some. Good luck.
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post #5 of 7 Old 10-21-2012, 10:37 AM - Thread Starter
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That's awesome, thank you! Looks like the crosstalk distance is about the same as it is for my monitor, then. Three feet is eye-blisteringly close for a TV that size, I can't see myself doing that in any event. So a distance of around 8-9 feet seems about right (which is how my current TV is set up downstairs, but it's only 47" and not 3D).

Appreciate the info, thanks!

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post #6 of 7 Old 10-21-2012, 12:44 PM
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You're very welcome, and I hope others will chime in on this subject.
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post #7 of 7 Old 10-29-2012, 06:42 AM
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I have the Vizio 47" passive 3D (E3D470VX) and the distance from coach to screen is some 8-9 feet away and that's perfect. If I get closer than 6 feet, the 3D starts to be very hard to watch...

BTW, all that talk that passive TV have half the vertical resolution in 3D is just nonsense - from the distance that 3D effects are comfortable to view, eyes cannot resolve the 'FullHD' resolution anymore. Based on formula from here, the full 1080 resolution on a 47" TV requires a maximum 54" viewing distance in order for the human eye to be able to see all those 1080 lines. That is 4.5 feet.
At 9 feet, for the same 47" screen, the eye can resolve only 1/2 of those lines, that's why passive 3D works so well.
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