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Spanky Ham
Joined: 22 Mar 2006
Posts: 5643
Location: Comedy Central
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| Posted: Tue Aug 27, 2013 2:15 am Post subject: |
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I am glad Crabb chimed in, so I could abbreviate my post. The only correction I would make is that I don't think a CRT is up near 50 MTF at 1080p. When I measured it at VDC with a 9500, IIRC it was around 30 or so. It is in a post over at AVS somewhere. IIRC MTF didn't become higher till we got down to like 1024x768.
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Tue Aug 27, 2013 2:25 am Post subject: |
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| ecrabb wrote: | | hal wrote: | | I think that it was Case that recommended rotating the CRT tubes 90 degrees and then moving the yokes back. Has anyone tried this in other setups? We would then have enough raster to get the 2160? |
I don't see how rotating the tubes really nets you anything. You do get a touch more vertical resolution to make for a sharper 2160, but then you have less width resolution. With a 10% blend overlap on a 3840 signal, you'd need roughly 2112w x 2160h on each projector - practically square. What does turning the tubes really accomplish?
| ElTopo wrote: | | A 909 resolves Full HD (1080p) 100% ! |
"Resolves 1080p 100%" is somewhat useless in this context. When people bat that phrase around, they mean they can see scan lines or see vertical lines, but in terms of real MTF, it's nowhere near 100%, but a bit better than half that.
There are razor sharp DLP projectors that can display 1080p on/off line pairs (both horizontal and vertical) and their MTF is in the 90% MTF ballpark. The production JVC LCoS machines are in the 80% ballpark give or take, and have gotten better. CRT is probably in 50% ballpark. The lower MTF is one of the reasons people (myself included) love the silky-smooth "film-like" image of CRT.
I remember Scott (tse) saying the better CRT lenses are in the ballpark of 11 or 12 line pairs/mm at 50% MTF. By my calculation, that means that the best 9" CRT projectors are going to be running out of MTF steam in the 2k x 2k resolution ballpark. That makes them very good machines for 1080p, but going higher than that is going to mean diminishing returns.
Given that, I think 4k on a blend is probably doable for somebody who has really excellent setup skills and is willing to put the time and money into it. It won't be "sharp" by any means, but I think with good content, it would be a significant improvement over a 1080p blend.
A single projector on the other hand I think would be a waste of time. Between the electronics and lenses, MTF would certainly be below 25% in both directions, (but especially horizontal) nearly eliminating any of the advantage of running 4k in the first place.
Running 4k on a G90 would be like running 1080p on a 1272. You can certainly send the signal, and you may even be able to get the projector to display it, but you're only going to see about half the resolution, so what's the point? Not trying to be wet blanket; it's just my opinion from all the reading over the years.
SC |
not even an opinion but just plain facts, i am not nearly as long as you around on this forum but already tired of typing down these same explanations over and over again.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Tue Aug 27, 2013 2:37 am Post subject: |
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Here is TSE's comment on CRT 9 inch lenses( the better ones)
http://www.avsforum.com/t/633597/wtf-is-mtf
The better CRT lenses are rated at 10-12 line pairs per mm at a certain MTF. I'm guessing here but I think you get your line pairs from a piece of glass that has lines of metal deposited on it (ronchi rule). Twelve strips of metal seperated by equal width of clear glass in a mm. This is placed where the phosphor normally is and lit from behind by a lamp. This is projected on a screen and the MTF measured. Have never seen it done but would like to one day.
And Rolands follow up comment
9" lenses are 150mm wide, so 12lp/mm will be 150*12*2 lines which is 3600 horizontal pixels. Standard HD10 with 10lp/mm will be up to 3000 horizontal pixels.
Of course this is at some MTF number (80%, 50%, whatsoever) which will already start to degrade the picture visible. But at 2/3 of the max resolution (1920/3000) even the plain HD10 should do a VERY good job.
Even 2500x2000 should be no problem, as 3000x2400 should be for the GT17.
Roland
Athanasios
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Aug 27, 2013 3:13 am Post subject: |
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| ecrabb wrote: |
No, UHD isn't 4k. It's a misnomer. In the production industry, 4k has a very specific meaning: 4096x2160 for native DCI, and 4096x3112 for full-aperture 4k. There were a couple of variants, but 4k generally meant 4,096 pixels.
The CE industry then tried to use the term, until they realized it was confusing for professionals and consumers, and it made no sense anyway, so they coined the "Ultra HD" term and started calling Ultra HD "4k Ultra HD" or "4k UHD" in the short-term. Long-term, no doubt, everyone will just refer to the 3840x2160 CE format as Ultra HD or UHD.
UHD has no business being called 4k, as it offers 94% of the resolution of 4k, and requires scaling to display true 4k content.
Sorry to be a pedant, but as technical people, we should be aware of the history and intricacies and not just reference the wiki definitions.
SC |
All true and all agreed. Its a much bigger difference than its made out to be. Being that this is going to be showing consumer content, discussing the ability to do 4k is somewhat irelevant, as its Ultra HD that will be getting displayed.
It wasnt me that said to flip the tubes in this instance, wouldnt be worth the effort.
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noos@xp37+
Joined: 17 Jun 2008
Posts: 464
Location: Berlin/Munich
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| Posted: Tue Aug 27, 2013 6:15 am Post subject: |
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| stridsvognen wrote: | Do any of you Guys have bandwidth to resolve 1080P72hz with no softening, and no loss in color dept.?
And whos running a blend with native 4K source and capable scalers and blend unit.? |
Yes, I do a lot of 4k...ups Ultra HD (or as I call it consumer 4K)
http://www.youtube.com/playlist?list=PLhLp7Kp-iLM0HpHI83ApTNfNW2EYwmAC6
http://www.youtube.com/playlist?list=PLhLp7Kp-iLM1WNLvmUJ8FsctBidV9qHQN
...on many devices, so I did tests on CRTs.
Make some test for your own and then reports your findings here. Use your Nvida graphic card and add the custom resolution of 2xxx X 1600p with 48hz/50hz/72hz (whatever you want to run on the horizontal in a blend). Or 2xxx X 2160p 48/72hz. Take care to to hit the 400mhz RAMDAC limit.
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Aug 27, 2013 7:40 am Post subject: |
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Why would you run at 4096 width for 3840 actual resolution?
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noos@xp37+
Joined: 17 Jun 2008
Posts: 464
Location: Berlin/Munich
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| Posted: Tue Aug 27, 2013 9:03 am Post subject: |
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Add as many horizontal pixels as you like to one half of 3840. That is what I mean with 2xxx horizontal resolution.
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Aug 27, 2013 9:04 am Post subject: |
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That wasnt my question!!
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noos@xp37+
Joined: 17 Jun 2008
Posts: 464
Location: Berlin/Munich
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| Posted: Tue Aug 27, 2013 9:28 am Post subject: |
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Sorry...
but to what do you refer? Where do I 4096 for a 3840 output. If you refer to games, I can render them in any resultion of a attached panel.
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Aug 27, 2013 9:41 am Post subject: |
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Games are fine, but they would be no point running in 4k for UHD content, unless you like black boarders and interpolation?
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