Why does...?

[Fzero]

Why does an LCD screen show inverted colour when viewed at slight [~45 degree] angles?

I searched this and got an answer http://blogs.plos.org/mitsciwrite/2013/05/02/your-computer-screen-from-an-angle/

But reading that, I still didn't quite get it  :unsure:

If you tilt it away from you, at ~45 degree it starts to become inverted and unplayable.

But, if you tilt it towards you, the image actually remains pretty good and is still playable.

This is not actually anything to do with the screen itself, right?

Otherwise manufacturers could rotate them and allow for a tilt away to still be playable.

So can anyone explain exactly, but in fairly simple terms, what is it that makes the screen only show that way [tilt toward]?

From reading that link, the forth paragraph from the end, talks about the horizontal slits of a screen causing the effect when looking above/below. But on most screens I see, like the Revo's screen, it's only when tilted away that it messes up, and tilting towards doesn't have the same result.

You know how it is when you notice something and just bugs you, especially when you can't understand exactly why

 

[ible]

my laptop screen is the opposite:  if you tilt it away from you, things are still readable, but if you tilt it towards you, it's not.

apparently there's a directionality involved that we should get right for the pyra too!

 

[pmprog]

The best way I can describe it based on that is imagine three sport stadiums next to each other, all with retractable roofs (in two pieces, split down the centre).

So you can have the roof closed (both pieces pushed together at the

______ ______ ______
/ || \ / | | \ /| |\
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\__||__/ \_|__|_/ \|____|/
Closed Halfway OpenWhen it's open, it lets the staidum light out up into the night sky. When it's halfway, it's same, but the angle the light is exposed at is restricted

______ __||||__ \\||||//
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Closed Halfway Open
Consider looking down across all three at about 45deg. You'll see that the half-way open ones, you'll receive less light because the "roof" is partially covering the line to your eyes.

Now this doesn't really describe why red and blue become prominant in a particular direction - but I'm assuming this is because depending what side of the three stadiums you're on, you'll get "brighter" light from the closest, and maybe the pixel colours are arranged vertically?

 

[Fzero]

I like this stadium scenario

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Halfway but with my red eye viewing from here

< __||||__
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Halfwayor from here

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HalfwayI'd expect the same amount of light/blockage of light ... if you tilt toward or away, as you're still getting same roof covering the line of sight.

Unless, the roof was angled I guess [so those horizontal lines on an LCD], that would cause a difference from one way [tilt toward] to another [tilt away].

And if that was the case, where the lines of an LCD were slightly angled and that's what caused it, they should be flipped around when being installed so that the tilt away was the unaffected tilt, as naturally I think that way is more natural to happen.

I'm sure that's not the case though, and if I were to get home tonight and hold my Revo upside down, the tilt away will still be the one that gets inverted/unplayable.

....bloody science and stuff!

 

[pmprog]

Yeah, there's only two "answers" I can think describe why, but I'm not sure how accurate they are.

Firstly - If you grabbed a blue torch and a red torch and pointed them both at you, but had the red slightly in front of the blue, I would guess you'd see more red light than blue; but I've not tried that so I could be wrong

Secondly, if the "roofs" are slightly curved

___________ ___________
/ \ / \
/ \ / \
| Red | Green |then any red travelling right from this diagram would be obscured by the green

Edit: Hmm, reading a bit more, sounds like the segments might be rounded, and have a rolling shutter:

they rotate it part of the way, and only let 50% through

 

[levi]

I don't fully understand LCDs, but I understand enough to say it's about the polarisation of light - liquid crystals work by flicking the direction of their polarisation depending on the voltage applied.

I'd guess a TN matrix panel which suffers the inversion problem does so because alternate lines are polarised inversely, but if you view at such an angle that you see the cell on the line below, you see a polarised source that's itself polarised inversely, so off gets translated as on and vice versa.  But that's only a guess, and doesn't explain why hues are not also inverted on my currently display, only intensity (saturation).

 

[rygD]

Why does...the title of this thread not give any hint as to what is being discussed?

I was going to mention the same stuff Levi mentioned.  That is my best guess based on past experience playing with polarization film and such with LCDs.  To fix the issue of tilting the screen and not being able to see what is being displayed, I think the display would need to be physically rotated.

 

[levi]

Generally, LCD TN matrix displays are oriented so that there's no distortion on the horizontal (or at least not major distortion), so you can share the display between people sitting next to each other (or arrayed around the room in the case of a TV set).

Generally TVs use IPS displays though which somehow don't have the same tint changes depending on angle.  I've no real idea how those are different to TN matrices in their construction though.  As do tablets and phones which these days are designed to be rotated.

 

[ible]

Why does...the title of this thread not give any hint as to what is being discussed?

i was going to write this exact thing myself.  my old boss would have been very unhappy with this thread/title if it was an e-mail/subject line.

 

[Fzero]

Why does...the title of this thread not give any hint as to what is being discussed?

I was going to mention the same stuff Levi mentioned.  That is my best guess based on past experience playing with polarization film and such with LCDs.  To fix the issue of tilting the screen and not being able to see what is being displayed, I think the display would need to be physically rotated.

I intentionally kept it that way, so it can be used for other general "Why Does" questions by anyone else.

When starting the post I did think to actually mention that too, so this thread can remain even once this particular question was answered ... but whilst writing my post I forgot to add that bit of detail. But yeah, anyone feel free to derail this original Why Does? and ask any other Why Does? questions

Why does...the title of this thread not give any hint as to what is being discussed?

i was going to write this exact thing myself.  my old boss would have been very unhappy with this thread/title if it was an e-mail/subject line.

Ha! Nevermind, but if it really bothers people I'm fine with the subject being specific to this one single question.

Also, I have my Revo now, and the screen does only invert one way.

So, it seems to me that a lot of these manufacture's who use LCD screens are placing them in upside down.

If I flip my Revo upside down, I can tilt it now away from me, and the viewing angle good now ... and when I tilt towards me it messes up.

So seems that these issues are screen related rather than environment or perception.

Wonder why they are not placed the other way during manufacturing, or if the slight angle that someone might be playing/viewing isn't even considered?

Like sat here at my desk, hands resting on the desk, the natural 45 degree angle ... when the device is held upside down ... is perfect [though of course can't actually play like this way up]

Edit:  Dear Revo, love the K101 ... but please for future models can you flip the screen when making them