# Computer privacy screens - how do they work?
**URL:** https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901
**Category:** Factual Questions
**Created:** [August 10, 2009, 2:00am UTC](https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901 "2009-08-10T02:00:28Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)
#### Post date: [August 10, 2009, 2:00am UTC](https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901/1 "2009-08-10T02:00:28Z")
At the public library the other day I was intrigued by the privacy screens they have on the computer terminals, such that viewing a monitor from any angle other than head-on is completely blacked out.
I googled “computer privacy screen” and came up with [this](http://www.tech-faq.com/computer-privacy-screen.shtml) which says:
> [@](#):
>
> In general, computer privacy screens are thin pieces of plastic material that easily fit your type of computer display. These filters have either very small louvers or panels that make viewing the screen at any other angle than directly in front of the monitor distorted.
OK, but I’m slow and need a diagram to really understand how that works. Since viewing the screens at an angle made them black to me, these panels must be absorbing light from those directions somehow while letting it pass through normally from a point straight ahead. But how exactly? What do these panels look like close up? And how would one that simply blurs the image vs. one that blacks it out differ?
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### Author:  [@Joey\_P](https://boards.straightdope.com/u/Joey_P)
#### Post date: [August 10, 2009, 2:07am UTC](https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901/2 "2009-08-10T02:07:51Z")
Like [this,](http://www.flickr.com/photos/andrew-turnbull/3773313080/) but smaller.
This is a stop sign that is designed so that a road the runs at a narrow angle to yours can have stop sign on it. The panels or louvers are pointed at the other street effectively blocking the stop sign from your angle.
Does that make more sense?
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### Author:  [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)
#### Post date: [August 10, 2009, 2:17am UTC](https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901/3 "2009-08-10T02:17:38Z")
> [@Joey\_P](#):
>
> Like [this,](http://www.flickr.com/photos/andrew-turnbull/3773313080/) but smaller.
>
> This is a stop sign that is designed so that a road the runs at a narrow angle to yours can have stop sign on it. The panels or louvers are pointed at the other street effectively blocking the stop sign from your angle.
> Does that make more sense?
Ah ok, so it’s just a simple opaque barrier. I was trying to imagine something more complex. And I take it if it’s a blur instead of black-out screen, then the panels are translucent?
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### Author:  [@Joey\_P](https://boards.straightdope.com/u/Joey_P)
#### Post date: [August 10, 2009, 2:22am UTC](https://boards.straightdope.com/t/computer-privacy-screens-how-do-they-work/505901/4 "2009-08-10T02:22:21Z")
> [@Rigamarole](#):
>
> Ah ok, so it’s just a simple opaque barrier. I was trying to imagine something more complex. And I take it if it’s a blur instead of black-out screen, then the panels are translucent?
That would make sense but in reality I have no idea. In fact even though that’s how I guessed they work (we have stop lights around here that you can only see from a specific angle) I have to say I never really gave it all that much thought. As soon as I read the description the stop sign was the first thing that came to mind. Even if it’s not exactly how it works, I assume it’s a close approximation.