CurtPalme.com Home Theater Forum

ElTopo · Joined: 07 Nov 2006 Posts: 1640

Hi all,

did someone ever tried to use a CRT in combination with a deflection mirror ?

cheers
ElTopo

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Yes, see e.g. http://www.curtpalme.com/forum/viewtopic.php?p=488277#488277

Works best if you can get a first-surface mirror, otherwise you get slight ghosting from the front-surface reflections.

**Curt Palme** · Posted: Wed May 06, 2020 2:04 pm Post subject:

Sure, Draper screens and other companies offer these systems, and I've seen and serviced a few installations back in the day. As Gary says, you need a super high quality optical grade mirror, which aren't cheap.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Guys

Avoid stretched mylar at all costs; it totally sucks. Never flat and sh*tty focus.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Best way to get a first-surface mirror is to cannibalize one from an old abandoned/junked rear-projection CRT TV.

Pantin93 · Joined: 17 May 2009 Posts: 5 Location: France/Paris

Yes, it works very well.
I've been using for years with first mirror surface (visible surface:31,5" x 15").

ElTopo · Joined: 07 Nov 2006 Posts: 1640

Nice.

Could you give some more details about the mirror ? Does it have a special surface ?

thanks
ElTopo

Pantin93 · Joined: 17 May 2009 Posts: 5 Location: France/Paris

It's a 5 mm glass thickness mirror. The front surface is the reflective (aluminium?) surface and behind, it's the glass.
A conventionnal mirror (second surface mirror) is the opposite: The glass is on top and the aluminum behind.
The reflection is like this:

As you can see, on a second surface mirror, there is a ghosting reflection.
And on first surface mirror, as it has no protection, we have to handle it carefully.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Guys

First surface is preferred; clean sparingly and maybe dust with canned air, it is easy to scratch.

robin36mac · Joined: 24 Jan 2009 Posts: 46

I used such setup in the past with a 808
I ordered the mirror on FirstSurfaceMirrors.com and it was about ~200$ without shipping&handling

Robin

**AnalogRocks** · Posted: Tue Mar 09, 2021 10:50 pm Post subject:

You can make your own first surface mirrors by removing the paint from the back of the mirror coating

mp20748 · Posted: Wed Mar 10, 2021 1:19 pm Post subject:

Mirror bounce is very possible, but not good for best image from HD sources, and expect some light loss and elevated black levels

pureaudio · Joined: 29 Mar 2015 Posts: 37

mp20748 · Posted: Wed Mar 10, 2021 5:15 pm Post subject:

yes, very much similar or same thing.

In a proper mirror bounce setup, the room (environment) has to be painted a very special FLAT black. The room also must not have any shiny, reflective or small light source (LED's, CRT filaments, etc. It has to be PERFECT black to even achieve the very slightest ANSI or Low end performance.

I maintained a Immersive (Stereoscopic) CUBE setup that was three 10 foot screens and the floor. All three screen projectors were direct to screen. The floor was an over head mirror bounce to the floor from an over head projector. The four projectors were Christie Digital Mirage DLP.

The customer (Navy) complained that they could not see the flight deck on a carrier to land a plane. It was a mission impossible, because the setup was in a very large multiple use open room that made it near impossible to create or maintain complete black for the setup.

The better setups used very thick glass first surface mirrors that were about an inch thick and was VERY expensive because they were custom ordered and manufactured at a lens factory.

So a proper for HD mirror system would require a Perfect Black projector environment and solid first surface glass mirror (very expensive), and still you can kiss any usable contrast ratio good bye.

The higher end better systems did not use mirrors. They were direct to screen rear projector setups that also required Perfect Black projector environments. The use of an overhead projector/mirror for Immersion (three screens and the floor display) where the three screens were direct projector shoot, were high level setups, because the floor was not a primary viewing surface, the floor display was only needed to help create the floating image (immersive) system.

That plastic stuff is terrible. It will collect dust on its surface that CANNOT be removed, meaning you'll always have a diminishing display system.

pureaudio · Joined: 29 Mar 2015 Posts: 37

mp20748 · Posted: Thu Mar 11, 2021 3:26 am Post subject:

I only mentioned "CRT filament" to let the OP know even the glow from a CRT filament would affect a Perfect dark room setup.

The mentioning of a CUBE was because a CUBE is the ONLY sensible use for mirror setup, and only for the above/floor display where image quality is not a concern:

"[b]The higher end better systems did not use mirrors[/b]. They were direct to screen rear projector setups that also required Perfect Black projector environments. The use of an overhead projector/mirror for Immersion (three screens and the floor display) where the three screens were direct projector shoot, were high level setups, because the floor was not a primary viewing surface, the floor display was mostly needed to help create the floating image (immersive) system.."

I did however mention Christie Digital Mirage (DLP) projectors, because ONLY a Digital Projector would make sense for ANY mirror bounce, where a CRT would produce a more distorted second image...

to be more to the the point, CRT should Not be used in a mirror system. It lacks the light output to survive the light loss and lack the sharpness to survive how a mirror (any quality) would degrade the image.

And that is why I mentioned "The higher end systems did not use mirrors" - "The use of an overhead projector/mirror for Immersion (three screens and the floor display) where the three (MAIN) screens were direct projector shoot, were high level setups, because the floor was not a primary viewing surface, the floor display was only needed to help create the floating image (immersive) system.."

I've maintained some CRT CUBE Setups, that used CRT because the goal was for better low level black performance. But they were always a terrible idea all the way around. Something that would be more obvious on the CRT Flight Simulators that used Mirror Bounce for the side windows.

So CUBE was mentioned here concerning Mirror Bounce, because Mirrors should only be used for CUBE or other NON high performance display systems.

One may think a mirror would simply reflect an image, when it's near impossible to use a mirror that would not ADD some form of Distortion and Light Loss... The higher end Mirror Bounce Systems used very thick Special Glass (optical grade) First Surface mirrors and solid and very heavy frames to keep the mirrors stable, where a thicker more perfectly FLAT surface was needed to help control distortions. Regular glass, plastic/flexible surface mirrors distorts the image, where it's not that obvious when using a Digital Projector (better sharpness/light output advantage and less lens distortions issues from three non perfectly matched lenses)

pureaudio · Joined: 29 Mar 2015 Posts: 37

**kal** · Posted: Thu Mar 11, 2021 3:30 pm Post subject:

pureaudio · Joined: 29 Mar 2015 Posts: 37

**kal** · Posted: Thu Mar 11, 2021 4:15 pm Post subject:

Thank you for making the changes.

Kal