[jsaliga]

A discussion about the G90 is taking place in the Digital Forum in this thread.


Someone cites sources on AVS and in magazines that the G90 is best when used with a screen size up to 84" wide 16:9 AR.


I am not calling in the cavalry here, but I would like some the G90 gurus to shed some light on this claim and why it would or would not be true.


--Jerome

 

[Brett]

Hi Jerome,


While I'm no Guru, not even a G90 owner, I do happen to use its 9 inch predecessor, the Sony VPH-1292Q. It's specs are somewhat lower rated than those of the G-90, and it has less light output because both its Red and Green tubes are color corrected.


IMHO, the "relatively small" screen recommendations for big-gunned projectors were possibly made using sub-optimal resolutions and refresh rates. The higher the refresh rate, the more light hits the screen, making a slightly bigger size feasable at an acceptable luminosity. Also, if your screen is not a 4:3 aspect ratio (16:9 or 2.35:1) then you can go wider yet as it won't be using your raster in the same way.


A leading G-90 calibrator (Wm) recommends mounting this projector about 8% closer to the screen, to get both better sharpness and more reflected light, making a larger screen more feasable.


Hope this helps a little until the Pros chime in.


Cheers,

 

[Mike2]

This site has some interesting information re: screen size and brightness with the G90.

12 ft wide and still greater than 10 lumens on the screen.

http://www.xtremedtv.com/torus.htm

 

[Ted White]

I posted a little bit on that thread. Suffices to say that an 84" max is silly.


The G-90 is super bright at 350 lumens. That's measured, by the way, not some theoretical spec for the purpose of literature.


Ted

 

[Deniz Mutlu]

Hey Ted,


Silly is right! Remember the images you saw at the TAW booth (last Cedia) displayed from our HD-800 8" gun CRT on the 96" wide screen. The G-90 should display a beautiful image at that screen size couple with the right video processor

 

[odyssey]

The screen size is a matter of personal preference, depending on how you rank different aspects of image quality. You really have to determine the minimum image luminance that you find acceptable. The most common standard is about 12 fL, although the image will continue to improve to at least 20 fL on HT size screens, where fatigue starts.


If you want a fairly uniform screen, a 1.3 gain is typical. Although the G90 will start out at 325-350 lumens, after about 6-12 months of average use, that will decrease by at least 25%. After another few months, the drop will be at least one third.


You can check the math, but if you want to have 12 fL for 100 IRE video on a 1.3 gain screen (no perf) after the projector ages some, an 84" wide screen is no longer that silly.


Some people clearly prefer a larger image at 8-9 fL, but I hope that they made that decision after seeing a smaller image at higher luminance. A smaller screen also allows a lower contrast setting that increases the resolution, gray scale tracking, and CRT life.

 

[wm]

Oh, I have to respond to this one. I respectfully ask where you get that 25% drop in light output for 6 months? And 1/3 drop in another few months? Sorry, I've got lots of measurements in my database that completely disagree with what I would have to surmise is speculation...


I just recalibrated a G90 for a customer that had over 900 hours on it, and it was putting out the same light output that I measured when I first installed it.


The G90 I have here has over 1000 hours on it, the first several hundred at a couple of trade shows, and it also shows no significant sign of wear. I can easily get over 17 ft lamberts from it on my 80" wide 1.3 gain microperf screen (it's a small room!). That's 350 ANSI Lumens, folks...


The G90 in the Faroudja booth at CEDIA was projecting onto a 111" wide 1.3 gain Stewart screen (non-perf). That projector also had been used at at least 2 other trade shows. I measured over 10 ft lamberts reflected when running at 1080p.


William

 

[odyssey]

William,


I have to admit that I don't have data to support the light output drop with aging for G90s. Your experience showing no drop at all is very surprising and I really don't understand why it would be different compared to other CRT projectors.


I just installed my G90 a few days ago and I will keep a log of light output. I hope you are right.

 

[wm]

Odyssey,


That projector has some pretty impressive crt's - I just re-calibrated one that had been originally installed at the Pjcalc throw distance, and then had to be moved to a new location. In the process of re-installing it we used my throw distance, putting it closer to the screen and thus using more of the crt phosphor. The projector had some 650 hours on it, and I expected to see a bright box around the image where the (until now) unused phosphor was. There was absolutely NO sign of any wear on any of the crts.


William

 

[REW]




Whats that sound?


"Old wives tales crashing to earth!"

 

[Per Johnny]

Theese screen sizes for a crt seems very big to me, but I don't say it isn't possible. I am only worried about the risk for crt wear and fast degradtion of picture quality. Is there some of you gentleman's with G90 experience that have checked a G90 with let us say a 100" wide sceen after 1000, 2000, 5000 and 10 000 hrs of use and can tell us the condition of wear, focus and light-output?


Per Johnny Ødegaard

 

[MikeM]

I have a 100" wide screen, but its been 15 months since the G90 was installed and i've only accumulated 420 hours so I really don't qualify for your poll. I don't have access to a light measurement device either, but my eyes tell me the picture is as bright as the day I first turned it on when there was only 17 hours on it.