LCD screens and polarization

You may recall that about two months ago I mentioned that my iPad's screen
is polarized so that when I look at it while wearing my polarized
sunglasses, the screen is blanked when held vertically.

I did a bit of experimentation at the Apple Store. My iMac (mid 2006
model) blanks when I turn my head sideways, as does the new 15" (non
retina) MBP. The retina MBP is also polarized, but at a 45° angle. (So is
the LCD display on my Prius.) My iPod Nano (current generation) is
polarized when tilted about 15° from having the controls and connectors to
the sides.

My iPhone, though, merely shows color artifacts regardless of orientation.

I didn't get around to testing any other iPods, the 13" MBP, any MBA, nor
the 30" stand-alone monitor.

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In article <michelle->,
Michelle Steiner <> wrote:

> You may recall that about two months ago I mentioned that my iPad's screen
> is polarized so that when I look at it while wearing my polarized
> sunglasses, the screen is blanked when held vertically.

*EVERY* LCD in existence is polarized. It's a side-effect of how they
function. The only question is which way you have to turn each one to
get it to "go blank" or otherwise distort while wearing your particular
pair of polarized shades.

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In article <js3fi8$f7o$>, Don Bruder <>
wrote:

> > You may recall that about two months ago I mentioned that my iPad's screen
> > is polarized so that when I look at it while wearing my polarized
> > sunglasses, the screen is blanked when held vertically.
>
> *EVERY* LCD in existence is polarized. It's a side-effect of how they
> function. The only question is which way you have to turn each one to
> get it to "go blank" or otherwise distort while wearing your particular
> pair of polarized shades.

Well, in the case of the iPhone, it doesn't go blank regardless of which
way you turn it. I was pointing that out as well as the orientations to
blank the screens of the other devices I mentioned. I was in no way
suggesting that those were the only LCD devices that are polarized.

--
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Michelle Steiner wrote:

> Well, in the case of the iPhone, it doesn't go blank regardless of which
> way you turn it.

With my polarizing sunglasses, I can see the iphone 4 partially going
blank at a certain angle. But not all of the screen is affected.

Would be interesting to find out why a retina display does not seem
polarised in any one direction as other LCD displays are.

Perhaps the density of pixel is such that the light is already polarised
as it passes through the dense pixels and there is no need for polarised
glass above it.

Salut Michelle

In article <michelle->,
Michelle Steiner <> wrote:

> I didn't get around to testing any other iPods, the 13" MBP, any MBA, nor
> the 30" stand-alone monitor.

Apple sells a 30" monitor where you live? They seem to have shrinked it
to 27" in swiss Apple Stores.

Cheers
Andreas

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In article <andreas->,
Andreas Rutishauser <> wrote:

> > I didn't get around to testing any other iPods, the 13" MBP, any MBA,
> > nor the 30" stand-alone monitor.
>
> Apple sells a 30" monitor where you live? They seem to have shrinked it
> to 27" in swiss Apple Stores.

I didn't test the monitor, so I didn't realize that the new monitors were
only 27" and not the 30" of a former model.

--
Tea Party Patriots is to Patriotism as
People's Democratic Republic is to Democracy.

In article <4fe566d7$0$49839$c3e8da3$ om>,
JF Mezei <> wrote:

> > Well, in the case of the iPhone, it doesn't go blank regardless of
> > which way you turn it.
>
> With my polarizing sunglasses, I can see the iphone 4 partially going
> blank at a certain angle. But not all of the screen is affected.
>
> Would be interesting to find out why a retina display does not seem
> polarised in any one direction as other LCD displays are.

But the retina displays on the iPad and the MBP are unidirectionally
polarized.

--
Tea Party Patriots is to Patriotism as
People's Democratic Republic is to Democracy.

In article <michelle->,
Michelle Steiner <> wrote:

> In article <js3fi8$f7o$>, Don Bruder <>
> wrote:
>
> > > You may recall that about two months ago I mentioned that my iPad's
> > > screen
> > > is polarized so that when I look at it while wearing my polarized
> > > sunglasses, the screen is blanked when held vertically.
> >
> > *EVERY* LCD in existence is polarized. It's a side-effect of how they
> > function. The only question is which way you have to turn each one to
> > get it to "go blank" or otherwise distort while wearing your particular
> > pair of polarized shades.
>
> Well, in the case of the iPhone, it doesn't go blank regardless of which
> way you turn it. I was pointing that out as well as the orientations to
> blank the screens of the other devices I mentioned. I was in no way
> suggesting that those were the only LCD devices that are polarized.

Polarized sunglasses are vertically polarized because the reflected
'glare' from roadways and other objects tends to be mostly horizontally
polarized. Perhaps with your iPhone retina display Apple is somehow
using 'circular' polarization
<http://en.wikipedia.org/wiki/Circular_polarization> a much more
complicated phenomenon, but that's beyond the scope of my physic course
recollection.

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In article <fmoore->,
Fred Moore <> wrote:

> Polarized sunglasses are vertically polarized because the reflected
> 'glare' from roadways and other objects tends to be mostly horizontally
> polarized. Perhaps with your iPhone retina display Apple is somehow
> using 'circular' polarization

That is a possibility. Next time I see a 3D movie, I'll check it out.

--
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People's Democratic Republic is to Democracy.

On 6/23/12 10:19 AM, in article
fmoore-, "Fred Moore"
<> wrote:

> In article <michelle->,
> Michelle Steiner <> wrote:
>
>> In article <js3fi8$f7o$>, Don Bruder <>
>> wrote:
>>
>>>> You may recall that about two months ago I mentioned that my iPad's
>>>> screen
>>>> is polarized so that when I look at it while wearing my polarized
>>>> sunglasses, the screen is blanked when held vertically.
>>>
>>> *EVERY* LCD in existence is polarized. It's a side-effect of how they
>>> function. The only question is which way you have to turn each one to
>>> get it to "go blank" or otherwise distort while wearing your particular
>>> pair of polarized shades.
>>
>> Well, in the case of the iPhone, it doesn't go blank regardless of which
>> way you turn it. I was pointing that out as well as the orientations to
>> blank the screens of the other devices I mentioned. I was in no way
>> suggesting that those were the only LCD devices that are polarized.
>
> Polarized sunglasses are vertically polarized because the reflected
> 'glare' from roadways and other objects tends to be mostly horizontally
> polarized. Perhaps with your iPhone retina display Apple is somehow
> using 'circular' polarization
> <http://en.wikipedia.org/wiki/Circular_polarization> a much more
> complicated phenomenon, but that's beyond the scope of my physic course
> recollection.

Circular polarization is the only useful kind when metering light through a
camera internally, like a DSLR. It doesn't skew the reading like linear
does.