NEC XG: Optimum Screen Size

G'day Ken,


I am running a XG-1350 with HD144 lenses and have my throw distance ( measured horizontally from screen to centre of green lens ) set at 1.2375 times the screen width ie. 99 inch throw for an 80 inch wide image.


My normal screen res for watching movies and TV is 1440 x 810 x 50Hz in a 16:9 format. Note that I am using a HTPC and have been quite aggressive with the front and back horizontal porch settings to achieve this. As you go up in refresh rate and horizontal res it becomes more difficult to maintain that short throw distance ratio because you run out of horizontal image size adjustment.


So on my setup and using your 131 inch throw I could show a 105.8 inch wide image ( 121.5 diagonal in 16:9 format ).


I wouldn't advocate trying to eek out any more phosphur usage than this though, as you start to degrade edge focus at these extremes ( still quite acceptable though if you've got a solid astig & focus setup ). Extreme edge and corner convergence can also be a challenge when pushing the limits.


My suggestion would be to increase the width control and see how wide you can go. That will set the upper limit , assumming you don't have control over your porch settings.


Cheers


Russ

I reckon your nuts Br Ken.


There's a reason why NECs have tiny little wear patterns when installed professionally - the setup tables are wrong/ultra conservative.


For a start they are wrong for 16:9 screens - due to the trapezoid shape of the raster, a 4:3 image of the same width is bigger on the tubeface. Meaning for a 16:9 raster you need to go wider.


Then the tables are setup to avoid lawsuits, not to optimise performance.


I've seen Russ' setup, and believe me the image is nothing short of stunning. The XG will handle this throw distance, there's even another thread with a few guys with a cumulative total of 10,000hrs with maximised raster.


It's your XG, but in my opinion you are hobbling it.


If your not going to listen, why did you ask? At least go for 100" wide, or play around with your source and see how wide you can get it - don't blindly follow the manual.


Mark

Quote:
DON'T use the book's figures for the screen size or you'll BURN a small wear pattern and you'll be sorry later on. Us AS MUCH of the tube face as you can (within 1/8" of the horizontal edges of the tube) and put the projector where you want it and size the screen to that.

Thx Guys,


So far I have 96" wide with a 110" Diagonal. I'll try & move the beast, but it is a bugger once it is setup. I can probably mobe it 5 inces closer, so giving me more raster usage.


Gulp, Tiz not easy eh!


I am using a HTPC, so I have reduced the Front & Back porch to the max of the Raster I am using. But by the sounds of it I can use more raster.


Br Ken./

Quote:
Hey Ken ....


now that I know you're using a HTPC, I've attached the powerstrip setting I use for PAL and NTSC (film based) DVD playback. Try these and see how they go on your system. I have a nice black cave of a theatre and hense use the 47.952 refresh rate for NTSC and don't notice any apparent flicker.


When I was setting up my 135 I chose to exceed the factory voltage setting for horizontal output transistor calibration at a whisker above standard, but still within the variance allowed. Consequently, for the PAL setting below my image width setting ( projector ) is at +41 and for the NTSC setting it's at +61. There still a bit of leeway left in the NTSC settings though if you want to try reducing the porch settings further.


Here's a tip: connect the PC to a multiscan monitor, turn up brightness to max and then squish the horizontal/vertical size so you can see the raster extremes. Bring up a full screen test pattern and adjust powerstrip porches until the 'image' is centred within the raster. Works for me!

PAL Settings -- 1440 x 810 x 50hz

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PowerStrip timing parameters:

1440x810=1440,7,152,113,810,6,11,13,71902,1


Generic timing details for 1440x810:

HFP=7 HSW=152 HBP=113 kHz=42 VFP=6 VSW=11 VBP=13 Hz=50


Linux modeline parameters:

"1440x810" 71.902 1440 1447 1599 1712 810 816 827 840 +hsync +vsync

----------------------------------------------------------------------

NTSC settings -- 1440 x 816 x 47.952hz

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PowerStrip timing parameters:

1440x816=1440,40,152,96,816,2,4,14,69272,1


Generic timing details for 1440x816:

HFP=40 HSW=152 HBP=96 kHz=40 VFP=2 VSW=4 VBP=14 Hz=48


Linux modeline parameters:

"1440x816" 69.272 1440 1480 1632 1728 816 818 822 836 +hsync +vsync

----------------------------------------------------------------------


Cheers


Russ