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CRT with deflection mirror possible ?
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ElTopo




Joined: 07 Nov 2006
Posts: 1607



PostLink    Posted: Wed May 06, 2020 6:17 am    Post subject: CRT with deflection mirror possible ? Reply with quote


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Hi all,

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




cheers
ElTopo



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garyfritz




Joined: 08 Apr 2006
Posts: 12024
Location: Fort Collins, CO


PostLink    Posted: Wed May 06, 2020 2:01 pm    Post subject: Reply with quote

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.
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Wed May 06, 2020 2:04 pm    Post subject: Reply with quote

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.
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Tim in Phoenix




Joined: 21 Oct 2006
Posts: 4378
Location: Phoenix


PostLink    Posted: Wed May 06, 2020 2:12 pm    Post subject: Reply with quote

Guys

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




Joined: 08 Apr 2006
Posts: 12024
Location: Fort Collins, CO


PostLink    Posted: Wed May 06, 2020 4:37 pm    Post subject: Reply with quote

Best way to get a first-surface mirror is to cannibalize one from an old abandoned/junked rear-projection CRT TV.
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Pantin93




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


PostLink    Posted: Mon Mar 08, 2021 10:47 am    Post subject: Reply with quote

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


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ElTopo




Joined: 07 Nov 2006
Posts: 1607



PostLink    Posted: Mon Mar 08, 2021 12:56 pm    Post subject: Reply with quote

Nice.

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


thanks
ElTopo

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Pantin93




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


PostLink    Posted: Mon Mar 08, 2021 1:25 pm    Post subject: Reply with quote

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.

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Tim in Phoenix




Joined: 21 Oct 2006
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Location: Phoenix


PostLink    Posted: Mon Mar 08, 2021 5:36 pm    Post subject: Reply with quote

Guys

First surface is preferred; clean sparingly and maybe dust with canned air, it is easy to scratch.
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robin36mac




Joined: 24 Jan 2009
Posts: 44



PostLink    Posted: Mon Mar 08, 2021 7:46 pm    Post subject: Reply with quote

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
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AnalogRocks
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Joined: 08 Mar 2006
Posts: 26690
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Tue Mar 09, 2021 10:50 pm    Post subject: Reply with quote

You can make your own first surface mirrors by removing the paint from the back of the mirror coating
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mp20748




Joined: 12 Sep 2006
Posts: 5681
Location: Maryland

TV/Projector: 9500LC Ultra / Super 02 and 03 VIM


PostLink    Posted: Wed Mar 10, 2021 1:19 pm    Post subject: Reply with quote

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




Joined: 29 Mar 2015
Posts: 37



PostLink    Posted: Wed Mar 10, 2021 4:15 pm    Post subject: Reply with quote

mp20748 wrote:
Mirror bounce is very possible, but not good for best image from HD sources, and expect some light loss and elevated black levels


Elevated black and light loss points in 2 different directions, if you have light loss it apply the same factor to bright and dark image, i would worry more about the already low ansi contrast getting worse.
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mp20748




Joined: 12 Sep 2006
Posts: 5681
Location: Maryland

TV/Projector: 9500LC Ultra / Super 02 and 03 VIM


PostLink    Posted: Wed Mar 10, 2021 5:15 pm    Post subject: Reply with quote

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.
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pureaudio




Joined: 29 Mar 2015
Posts: 37



PostLink    Posted: Wed Mar 10, 2021 11:32 pm    Post subject: Reply with quote

mp20748 wrote:
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.


So what your saying is that a non mirror CRT setup dont need a well treated room for proper performance, and a mirror setup do?

Im not really sure the thread starter is going for a cube setup, so dont see the relevance, if the mirror reduce light on screen with 4% it will do so in the hole range, ambient light and room reflections is another issue.

No CRT setup can fully resolve a 1080P signal, mirror or no mirror, and if mirror setup is made properly its a limited negative effect in a single CRT projector setup, the biggest limitation is still the CRT projector itself.


Last edited by pureaudio on Thu Mar 11, 2021 4:02 pm; edited 1 time in total
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mp20748




Joined: 12 Sep 2006
Posts: 5681
Location: Maryland

TV/Projector: 9500LC Ultra / Super 02 and 03 VIM


PostLink    Posted: Thu Mar 11, 2021 3:26 am    Post subject: Reply with quote

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)
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pureaudio




Joined: 29 Mar 2015
Posts: 37



PostLink    Posted: Thu Mar 11, 2021 2:47 pm    Post subject: Reply with quote

mp20748 wrote:
I only mentioned "CRT filament" to let the OP know even the glow from a CRT filament would affect a Perfect dark room setup.



How do the filament glow get through the cover?


Last edited by pureaudio on Thu Mar 11, 2021 5:50 pm; edited 1 time in total
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kal
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Joined: 06 Mar 2006
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Location: Ottawa, Canada

TV/Projector: JVC DLA-NZ7


PostLink    Posted: Thu Mar 11, 2021 3:30 pm    Post subject: Reply with quote

pureaudio wrote:
If you want to show proper HD image you dont run a CRT setup, CRT is history, and collectors items, nobody have a decent CRT setup that will do 16fl on a 120" screen, and resolve 1080P 8 bit from corner to corner, and today we run 4K.

This is the "CRT Projectors" sub-forum, for discussing CRT projectors. Your soap-box comments are not constructive and do nothing but insult. I don't run a CRT projector myself anymore, but many do and enjoy it, so please respect that and use some tact.

Not everyone may want 4K, 16ftL, or similar. That's their choice. That doesn't mean they should be belittled with elitist comments like "today we run 4K".

When we first added a "digital projectors" forum years ago we were strict and did not allow people to poke fun at or berate digital owners or their equipment as we had the opposite sort of "digitals suck" insults flying around. Nobody wanted to post in the digitals forum because inadvertently some elitist CRT owner would start insulting their choices. Not at all constructive. The same goes for the CRT projector forum.

Thank you.

Kal

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pureaudio




Joined: 29 Mar 2015
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PostLink    Posted: Thu Mar 11, 2021 4:04 pm    Post subject: Reply with quote

kal wrote:
pureaudio wrote:
If you want to show proper HD image you dont run a CRT setup, CRT is history, and collectors items, nobody have a decent CRT setup that will do 16fl on a 120" screen, and resolve 1080P 8 bit from corner to corner, and today we run 4K.

This is the "CRT Projectors" sub-forum, for discussing CRT projectors. Your soap-box comments are not constructive and do nothing but insult. I don't run a CRT projector myself anymore, but many do and enjoy it, so please respect that and use some tact.

Not everyone may want 4K, 16ftL, or similar. That's their choice. That doesn't mean they should be belittled with elitist comments like "today we run 4K".

When we first added a "digital projectors" forum years ago we were strict and did not allow people to poke fun at or berate digital owners or their equipment as we had the opposite sort of "digitals suck" insults flying around. Nobody wanted to post in the digitals forum because inadvertently some elitist CRT owner would start insulting their choices. Not at all constructive. The same goes for the CRT projector forum.

Thank you.

Kal


Sorry not meant as a insult, just a few facts, changed the post, hope you can approve the changes.
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kal
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Joined: 06 Mar 2006
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PostLink    Posted: Thu Mar 11, 2021 4:15 pm    Post subject: Reply with quote

Thank you for making the changes.

Kal

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