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Discussion Starter · #1 ·
Should raster centering be accomplished with a 4:3 shape or 16:9? I have a 16:9 screen and have been using a 16:9 shape.


Also, how much usage of the geometry controls is permissible for raster centering? I normally use keystone and amplitude.


And, what the heck is DC Hlinear? Why is it not in the manual? It has no effect until a certain point and then a major shift to the left. Nothing incremental before or after.
 

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It really doesn't make any difference whether you are using a 4:3 or a 16:9 screen, the raster centering doesn't change.


As for the DC HLIN control, although you don't say what projector you're talking about, it's NOT a control for NORMAL setup or service and shouldn't have been touched.
 

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Quote:
Originally posted by Crescent
Thanks for the reply!


I've got an XG and dc hlinear is right on the alignment menu.


Is it OK to use keystone to make it somewhat square?
That's what "keystone is for, just try not to exceed the maximum projector angle and then have to use maximum keystone to correct it.


I believe the control you're referring to is to set the horizontal linearity.
 

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I rough out the geometry with linearity, and get the amplitude correct for the throw distance - before I centre them. Well sort of anyway - it's all iterative.


phase

rough geom

centre

check amplitude and adjust

astig

raster centering again

astig

check phase

tweak geom (amp, lin mainly) - to get centre of image in centre of tube/screen, AND corners equal distance from tube/screen edge. You need to get linearity correct to get this, cause that'll move the raster around on a NEC.

check centre

astig

drink beer

check geom

check centre

etc....


At the end you want good geometry with centred raster and image and a square projector. The setup guides make it sound like a step by step process, but I found I need to go back and forth all over the place - everything interacts...


After your've got this right, you can really get stuck into tweaking the thing ;)
 

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That's it Mark....scare the **** out of him. :D


By the way, how's my friend Bob and his G70, I haven't seen him around?
 

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Me neither, no Bob for ages.


It's not actually that hard - I ws just trying to make the point that you have to go back and forth a few times - takes 2 mins each step, not hours.


dc h-linear is an odd extra command added to NEC's at with the PG Xtra. It sort of does linearity, but is different somehow. (I think it was added to fix trouble with the classic 720p at 60hz timing). Basically if you can get good geometry without it, leave it alone. I think only Doug and Vern understand it properly....
 

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Discussion Starter · #8 ·
Thanks to all!


I think I can handle the "drink beer" part.


I've set this up before. I'm just trying to improve it and learn more.


It sounds like I shouldn't use dc-hlinear. In the past, I've used it.
 

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Ive used dc h-linear too, but I don't really understand what it does different to linearity...
 

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Mark, I'm still learning my way around my XG so this is probably a dumb question, but...


1st step: phase. Which phase? The cursor phase (which I think centers the test patterns, yes?), or the other phase?


Rough geom: do you mean doing the alignment on the green? (skew, bow, pincushion, etc.) And subsequently the convergence on red/blue?


Astig: I wasn't sure how much I was supposed to mess with the astig on an XG852. I had the impression I should leave it alone until I knew what I was doing much much better?


I can handle the "drink beer" part too, now I just need to practice the rest... :)
 

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As far as setting up the geometry, Doug Baisey, who is the expert on NEC projectors, recommends turning off the Red and Blue and getting the Green geometry perfect BEFORE going any further, otherwise it will never be right.
 

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Discussion Starter · #12 ·
Thanks to all!


As far as the topic goes, I was just trying to use enough geometry to do raster centering, not make geometry perfect before raster centering.


Also, I'd like to get to the bottom of the dc-hlinear. It doesn't make sense to me that they would put a setting on the alignment menu that was not supposed to be used. I'm not sure why this is such a big secret. It;'s not in any manuals. No one is talking about it....
 

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Quote:
I rough out the geometry with linearity, and get the amplitude correct for the throw distance - before I centre them. Well sort of anyway - it's all iterative.
Can someone point to a post that explains this or explain it here. Using geometry controls like keystone make perfect sense to me, but I don't see how you can accomplish the same thing with linearity and amplitude controls.


I can see the benefit in that you don't have to drive the geometry/convergence as hard.


I've also found the iterative and repetitive approach works best and I always get the geometry for green setup the way I like before I worry about the other two guns...
 

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Yes, you should get the keystone close I guess, but on the green tube there shouldn't be much keystone really - it's the widest raster corners you care about for centering.


And if you centre the rasters without roughing out linearity, when you do the linearity, your raster will no longer be centered.


Thats what I was trying to say.



As for phase - theres 3 parts of phase: centre test pattern, balance wiggle in the horizontal centreline (align wave forms I think) and align the bump in the centre (align point controls to image). This matches the phase of the signal to the phase of the internal waveforms.


Do some searches on phase, it's been covered before.
 

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Discussion Starter · #15 ·
Thaks to all.


I was able to achieve the sharpest focus I've ever gotton out of the projector. However, my geometry sucks. I guess it's not horrible and the picutre looks good. It's just not perfectly rectangular. I also have a little too much bend in one of the corners, but most people don't seem to notice. It's almost as if wide screen is so much for the eye to take in at center, that they don't notice the edges.
 
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