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Help stacking G90s

 
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Sat May 27, 2017 4:53 am    Post subject: Help stacking G90s Reply with quote


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I'm looking for the basic geometrical setup information that has been proven to work when stacking a pair of G90s. (Not blending, just stacking.)

A side by side stack is possible in my situation, a vertical stack really is out of the question.

I've been experimenting with two G90s on wheeled carts in my garage setup, and I know there's a satisfactory setup to be had but I haven't quite found it yet. Nothing seems to adjust far enough. I suspect it only works with extended throw distances.
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gregstv



Joined: 27 Aug 2007
Posts: 628
Location: Australia


PostLink    Posted: Sat May 27, 2017 6:18 am    Post subject: Reply with quote

Maybe search cliff's post. He had side by side G90 stack. At one stage he had a triple stack of G90s.
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Tim in Phoenix



Joined: 21 Oct 2006
Posts: 4263
Location: Phoenix


PostLink    Posted: Sat May 27, 2017 11:16 am    Post subject: Re: Help stacking G90s Reply with quote

cmjohnson wrote:
Nothing seems to adjust far enough. I suspect it only works with extended throw distances.


Kind of defeats the purpose huh?

Accelerated tube wear, iffy focus..........
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Sat May 27, 2017 11:56 am    Post subject: Reply with quote

Well, the extended throw distance means a larger image, and although dimmer, with two projectors throwing the image, I get my image brightness back. Net result is a larger picture at the same very acceptable brightness level. I can live with that.

It's not about brightness for its own sake. If that's the goal I'd buy one of Curt's 7000 lumen digital light cannons.
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jbltecnicspro



Joined: 23 Apr 2016
Posts: 504



PostLink    Posted: Sat May 27, 2017 3:44 pm    Post subject: Reply with quote

Out of curiosity, why stacking vs blending? Seems to me that blending would be a great way to deal with rooms that don't allow for longer throw distances.
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Curt Palme
CRT Tech


Joined: 08 Mar 2006
Posts: 23844
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Sat May 27, 2017 4:06 pm    Post subject: Reply with quote

More brightness with stacking, albeit at a loss of resolution, and projector drift is a bitch! Smile

Cliff's G90 stack was amazing though, minimal drifting.
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Tim in Phoenix



Joined: 21 Oct 2006
Posts: 4263
Location: Phoenix


PostLink    Posted: Sat May 27, 2017 5:30 pm    Post subject: Reply with quote

Curt Palme wrote:
More brightness with stacking, albeit at a loss of resolution, and projector drift is a bitch! Smile


More brightness?

Using 75% of the phosphor height?
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Sat May 27, 2017 9:16 pm    Post subject: Reply with quote

Yes, more brightness, simply because two projectors are illuminating the same space as one would. That is assuming that it's set up to stack for more brightness and NOT for a larger screen.

I believe there are certain limitations that require stacked G90s to either run smaller active rasters or larger screens. They just don't have the wide geometry adjustment range of say a Marquee Ultra. Ultras can be stacked at a much smaller throw distance.
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Tim in Phoenix



Joined: 21 Oct 2006
Posts: 4263
Location: Phoenix


PostLink    Posted: Sun May 28, 2017 2:09 am    Post subject: Reply with quote

Say CM

Curt's comment was after "Out of curiosity, why stacking vs blending? Seems to me that blending would be a great way to deal with rooms that don't allow for longer throw distances."

And blending is unbeatable for light output.
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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Sun May 28, 2017 2:17 am    Post subject: Reply with quote

I want to learn stacking as well as blending. But I can stack TODAY, and I don't yet have a blend solution.
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km987654



Joined: 25 Jul 2007
Posts: 2800
Location: Australia

TV/Projector: Barco BG809s


PostLink    Posted: Thu Sep 13, 2018 6:25 am    Post subject: Reply with quote

Happy to be corrected here but it seems that when stacking the light output for any square area (per square inch or cm) of a screen will increase whereas it will stay the same for a blended image. I have no doubt that total light from a blend goes up because more phosphor is used but for any square area of the projected image light output of a blended image would be the same as a single projector. Also resolution must decrease for any square area of screen with a blend so even though the image is larger the resolution reduces per projector. If you increase the light output for any square area of image you would also increase contrast.
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gjaky



Joined: 05 Jun 2010
Posts: 2688
Location: Budapest, Hungary


PostLink    Posted: Thu Sep 13, 2018 7:56 am    Post subject: Reply with quote

km987654 wrote:
Happy to be corrected here but it seems that when stacking the light output for any square area (per square inch or cm) of a screen will increase whereas it will stay the same for a blended image. I have no doubt that total light from a blend goes up because more phosphor is used but for any square area of the projected image light output of a blended image would be the same as a single projector. Also resolution must decrease for any square area of screen with a blend so even though the image is larger the resolution reduces per projector. If you increase the light output for any square area of image you would also increase contrast.


When you do a blend, you physically split your screen between the two projectors , so considering the same screen size for a blend and a stack (for the moment) then one blend projector would serve only roughly half of the screen (area) while a single stacked projector would serve the whole screen are with the same light coming out of the projectors. Therefore they would produce roughly the same light output (double of a single projector on that same screen). Bigger utilized phosphor area would not contribute to higher light output on the first hand (considering phosphor does not get saturated in any case, which would ruin your grayscale anyway), but for longer service life, and better resolution power.

_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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km987654



Joined: 25 Jul 2007
Posts: 2800
Location: Australia

TV/Projector: Barco BG809s


PostLink    Posted: Thu Sep 13, 2018 9:10 am    Post subject: Reply with quote

gjaky wrote:
km987654 wrote:
Happy to be corrected here but it seems that when stacking the light output for any square area (per square inch or cm) of a screen will increase whereas it will stay the same for a blended image. I have no doubt that total light from a blend goes up because more phosphor is used but for any square area of the projected image light output of a blended image would be the same as a single projector. Also resolution must decrease for any square area of screen with a blend so even though the image is larger the resolution reduces per projector. If you increase the light output for any square area of image you would also increase contrast.


Bigger utilized phosphor area would not contribute to higher light output on the first hand (considering phosphor does not get saturated in any case, which would ruin your grayscale anyway), but for longer service life, and better resolution power.


Not sure I understand you here. If you light up more phosphor there would have to be more light in total.
My point is that per square cm of image there would be no more light output than a single projector.

How does using more phosphor increase resolving power?

Also if you split the image and project it over a larger area then the amount of image information per square cm would have to go down. So a 1080p image on a 100 inch screen (one projector) would have a more image information than the same 1080p image on say a 160 inch screen (two projectors).

I understand that the solution would still be the same at say 1080p no matter how big or small the image so I have altered the terminology to "image information". I practical terms the image on a larger screen at the same resolution would be subjected to pixalisation (if I can user that term with a CRT projector).
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gjaky



Joined: 05 Jun 2010
Posts: 2688
Location: Budapest, Hungary


PostLink    Posted: Thu Sep 13, 2018 10:12 am    Post subject: Reply with quote

km987654 wrote:

Not sure I understand you here. If you light up more phosphor there would have to be more light in total.


Keep in mind that light output is a function of the (peak) beam current on the first hand, and that is not depending off phosphor area, there are other factors like I said the saturation of the phosphor (ie, there will be no more light output even if the beam current increases), but this would limit the practical usage anyway. Phosphor degradation is depending on heat as it seems, and using a larger phosphor area will help to keep the phosphor cooler because the average current density is smaller for the given area (note here the emitted light is depending of the peak current mainly, but as a side effect heat is generated and this is averaged over the surface), more surface better heat spreading.


km987654 wrote:

My point is that per square cm of image there would be no more light output than a single projector.


When dealing with blend setups you inherently get twice as big screen, so either you get the same light/sq cm as a single projector, BUT on a twice as big picture, or vice versa, twice as much light/sq cm, on two "half sized" screen, because blended projectors will split the screen between the two of them anyway.

km987654 wrote:

How does using more phosphor increase resolving power?


Easily, consider the tube that has roughly 4:3 aspect ratio, but we project in 16:9 or even worse 21:9, in a blend you split your screen horizontally so you have two tubes in a virtual ~8:3 (=24:9) aspect ratio configuration, therefore you have to fit the same number of pixels on a much bigger area (on two tubes) that also have better matching "shape", in other words you can fit much more pixels to reach the same pixel density than it would be on a single projector.


km987654 wrote:

Also if you split the image and project it over a larger area then the amount of image information per square cm would have to go down. So a 1080p image on a 100 inch screen (one projector) would have a more image information than the same 1080p image on say a 160 inch screen (two projectors).


True, but as of now 4K phones, did not killed the flat panel TV market either, even though the image information per sq cm is less on the TV.

Seriously, in a blend especially on CRT is useful, because you will save on image bandwidth what each projector sees, that is also benefical.

km987654 wrote:

I understand that the solution would still be the same at say 1080p no matter how big or small the image so I have altered the terminology to "image information". I practical terms the image on a larger screen at the same resolution would be subjected to pixalisation (if I can user that term with a CRT projector).

True.

_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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View user's photo album (1 photos)
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