
How to Convert a Digital Watch to a Negative Display - zenburn
http://forums.watchuseek.com/f43/how-convert-plain-dw-5600-negative-display-129102.html
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jsingleton
Nice. I remember doing this to my scientific calculator at school.

Modern colour LCDs are still polarised, so I can only view my phone and tablet
in one orientation when wearing my polarised sunglasses. On the plus side,
they make for an excellent real life ad-block to those annoying video
billboards (which are just portrait LCD TVs).

I wonder how practical it would be to make a private display by removing the
polarising film from it and then viewing with polarised glasses.

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jrajav
> I wonder how practical it would be to make a private display by removing the
> polarising film from it and then viewing with polarised glasses.

It's been done, pretty much how you'd expect:

[http://www.instructables.com/id/Privacy-monitor-made-from-
an...](http://www.instructables.com/id/Privacy-monitor-made-from-an-old-LCD-
Monitor/)

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jsingleton
There are quite a few hacks around but I wondered if there was some reason
these aren't more widespread or commercially available. Business idea?

You could also make something that filters all light but near infra-red so it
could be seen by CCDs (on cameras or phones) but not with the human eye. Or do
the reverse and flood the picture with near infra-red to prevent it being
photographed.

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rcxdude
I think you can buy this kind of thing, I've seen them in use in some offices
where sensitive information is being viewed.

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dfc
It is funny and strangely comforting that despite such a wide variety of
topics, forum culture is still the same. There is always a large segment of
the forum population that derive some level of pride in listing their
collection of _X_ in their signature. Here we see posters list their "casios
in rotation," on the spyderco it is lists of knives and ubuntu forums it is
"rig specs" and version names. The puzzling thing is that--thankfully--this
does not seem to happen on mailing lists.

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bodhi
This is can actually be quite useful on "help me!"-style forums, like car
forums. People often forget to give enough info about eg. their car year
model, for others to help specifically. But if this info is in your sig, it's
hard to forget (but also you forget to update it when it changes)

> The puzzling thing

I'd guess that this is because forums have forum-specific profiles, whereas
mailing list are replied to from the one inbox.

Also, people can probably manage to find the signature section of a forum
profile, but not their (web)mail client!

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Domenic_S
Inkjet transparency sheets like you'd find at your local office supply store
[0] are polarized; you may not have to order polarizing film.

I used to own a car that had an LCD display where the orientation of the
polarization was perfectly set so if I was wearing my polarized sunglasses,
the screen was blank. I cut out a little overlay made out of an overhead
transparency and fixed the problem.

0: [http://www.officemax.com/office-supplies/presentation-
equipm...](http://www.officemax.com/office-supplies/presentation-equipment-
supplies/transparency-film)

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teekert
An overlay of other polarizing material won't change the polarization unless
your transparencies are somehow quarter wave plates?
([http://en.wikipedia.org/wiki/Circular_polarizer#Circular_pol...](http://en.wikipedia.org/wiki/Circular_polarizer#Circular_polarizers))

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robryk
If you have two perpendicular polarizers, no light will pass through both.
But, if you insert a polarizer at a 45 degree angle to both of them inbetween,
some light will pass through. Am I wrong?

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msandford
You are exactly right.

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dscpls
This is why I trawl the comment section.

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maaaats
I remember doing that to my calculator when I was a teenager. Thought my
unique calculator was badass then, hehe.

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mrtksn
Back then I hadn't access to the internet(1997-8?) and I was trying to figure
out how this LCD screen thingy was working by dissecting the parts of my Casio
clock and I found out about this "miracle" glass that looks just as normal one
but inverts the screen colors(=b&w) when put in different position. I have to
say, it made me a badass :)

Now-days kids could just look it up in minutes an move on. I am not sure if
this is a good thing.

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matthewmcg
Anyone know if the "cmoy" behind the howto mentioned in the OP is the same guy
(Chu Moy) that designed the CMoy headphone amplifier circuit?

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johnatwork
Related to the Polarization subject, when you are shopping for Polarized
sunglasses, then take two copies of the sunglasses and placed them so that you
are looking through both lenses, but one in 90 degree and notice if it turns
opaque-black.

Many times in the past when I was looking for some cheap polarized sunglasses,
I found that some were actually falsely labeled.

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zenburn
I was going to do it to my Casio GLX5600 but I realized it would reverse the
moon phases :(

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throwwit
Cut a separate piece out and flip it.

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jisaacks
According to the time difference in the before an after shots, it looks like
this takes ~4 hours to do?

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makomk
According to the post itself, 3 of those 4 hours were spent removing the glass
and then replacing it after realising it never needed to be removed in the
first place. If you skip that step it's probably a lot faster.

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pokstad
I've owned a Casio G-Shock that was negative by default (G-5600KG) and I found
that the viewing angle on a negative display was much more narrow than on a
positive. Most of the reviews on Amazon state the same. Anyone have an
explanation for this?

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deutronium
In a similar vein with a TFT screen
[https://www.youtube.com/watch?v=xUw3u9lh9rQ](https://www.youtube.com/watch?v=xUw3u9lh9rQ)

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aaronz8
Wow! I remember doing this to my and my friends' 4-function calculators in 5th
grade! This was actually how I learned how LCDs worked.

You can also remove the reflective sticker on the back of the black and white
LCD, to make it transparent where it was previously reflective. That's how I
made my calculator work with our classroom's overhead projector. (and some
really interesting pranks)

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Cthulhu_
That's a pretty neat hack. Reminds me of a DIY projector where an LCD screen
was stripped down and placed on top of an overhead sheet projector.

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rattray
Phosphor makes watches with E-Ink displays, so you can toggle between white-
on-black and black-on-white. I've been happy with mine, which I've had for a
couple years now:

[http://www.phosphorwatches.com/E-Ink-Digital-Hour-Clock-
Watc...](http://www.phosphorwatches.com/E-Ink-Digital-Hour-Clock-Watch-
Stainless-Steel-p/705105652801.htm)

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tomswartz07
I did this to my JVC car radio. It made it so much easier to read in the
sunlight.

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ttflee
I did this to my calculator, possibly a CASIO one.

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RBerenguel
I did this a lot to LCD gaming handhelds back in the early 90s. Also using two
polarising sheets to understand polarisation. Was very interesting, a pity
nowadays taking apart stuff is not so easy.

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ballard
I'm wearing a Newton Digital which is already negative in the default state,
and it seems possible to convert it to a regular positive display. Wouldn't
look as cool though.

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tlrobinson
I remember discovering polarization and how LCDs worked in grade school when
my calculator came apart and I accidentally flipped the polarizing film
around.

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motyar
I remember changing a digital clock to anticlockwise.

BTW good work.

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xchip
but.. Who hasn't done this?

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chrisBob
LCD monitors all use the same technology...

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nfoz
Fun office prank?

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ballard
Sounds more likely to shock the pranker than the prankee.

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lkd
The "magic" explanation doesn't satisfy me. Any physicists in the crowd who
can explain why rotating the film 90 degrees creates a negative display?

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darkmighty
It's actually really simple. The display works in a way that you control the
polarization of outgoing light (but the intensity is constant). Then you
filter whichever polarization you want. So a black dot on a white screen could
be achieved with a small vertical polarization region on a horizontal pol.
background, and filter out the vertical pol., with a polarizer horizontally
aligned. Align it vertically, and you swap the intensities.

Note: In this case the light whose polarization is controlled is the reflected
incoming ambient light, which isn't polarized; in a computer monitor it's the
back light.

