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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Mon Feb 23, 2009 4:10 am Post subject: |
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| nuttall_chris wrote: | | Mark_A_W wrote: | My XG will do it too.
Chris is bang on with the cause.
To fix it you need more porch pixels (I can't help with the Marquee specific retrace settings), and reduce the width/size setting.
More porch pixels/reduced width will mean that you may have to more the projector back...closer to the factory settings...to fill the screen.
If I want to eliminate the ringing on my XG at 1080i 96hz I really need to move the projector back. |
You can also add more porch pixels and then widen the raster. This will give you the same size image on the tube face eliminating the need to move the projector back.
Chris. |
There are limits - you run out of width. That's my problem. If I want to 100% fix the ringing, then I gotta move it back. Since I can't be arsed, I minimised the issue and ignore it. It's my choice.
The throw distances we used to use for DVD based res's or 1080i may not be suitable for higher scanrate HD.
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schmoe
Joined: 30 Mar 2008
Posts: 374
Location: Seattle, WA
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| Posted: Mon Feb 23, 2009 8:03 am Post subject: |
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| CIR Engineering wrote: | This is most likely the worst with 1080p right?
It's raster ringing, and all projectors that I have seen do it to some degree or another. The best fix to improve the situation is to position the image as far to the left (when looking into the tube) on the raster as you possibly can (away from the leading edge). The farther the edge of the image is from the start of the raster the more time the beam will have to settle down.
This happens with high scan rates because the beam has to go from -40 IRE all the way up to the image IRE level (and you are probably showing a 100 IRE field in the photo so 140 IRE jump?). When the beam does this, it shoots past the IRE level desired and then oscillates for a spell. That's what makes those waves in the picture.
If you are using a VP or HTPC you can do as others suggest and increase your porch sizes, to make the raster bigger, to allow for even further positioning of the image away from the edge. However, keep in mind that when you increase the pixel count you also draw more bandwidth and your image may become softer.
The G90 is the best projector in terms of being able to make this distortion almost invisible, but you can still see it if you know what to look for.
craigr |
Thanks for the very detailed explanation, Craig. Between shifting the raster to the far left and compensating via a VP/HTPC, which of the two methods do you prefer? You listed one con of the VP method being a potentially softer image. Are there any cons to shifting the raster? Would that give you uneven wear?
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Mon Feb 23, 2009 8:26 am Post subject: |
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| CIR Engineering wrote: | This is most likely the worst with 1080p right?
It's raster ringing, and all projectors that I have seen do it to some degree or another. The best fix to improve the situation is to position the image as far to the left (when looking into the tube) on the raster as you possibly can (away from the leading edge). The farther the edge of the image is from the start of the raster the more time the beam will have to settle down.
This happens with high scan rates because the beam has to go from -40 IRE all the way up to the image IRE level (and you are probably showing a 100 IRE field in the photo so 140 IRE jump?). When the beam does this, it shoots past the IRE level desired and then oscillates for a spell. That's what makes those waves in the picture.
If you are using a VP or HTPC you can do as others suggest and increase your porch sizes, to make the raster bigger, to allow for even further positioning of the image away from the edge. However, keep in mind that when you increase the pixel count you also draw more bandwidth and your image may become softer.
The G90 is the best projector in terms of being able to make this distortion almost invisible, but you can still see it if you know what to look for.
craigr |
You make it sound like a video chain issue Craig. Overshoot in the neckboards.
It's my understanding that it is a beam settling issue. The beam is oscillating: faster = dimmer, slower = brighter.
If it was neckboards it would happen anyway, not just on the LH edge.
Mark
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Mon Feb 23, 2009 1:28 pm Post subject: |
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| schmoe wrote: | | CIR Engineering wrote: | This is most likely the worst with 1080p right?
It's raster ringing, and all projectors that I have seen do it to some degree or another. The best fix to improve the situation is to position the image as far to the left (when looking into the tube) on the raster as you possibly can (away from the leading edge). The farther the edge of the image is from the start of the raster the more time the beam will have to settle down.
This happens with high scan rates because the beam has to go from -40 IRE all the way up to the image IRE level (and you are probably showing a 100 IRE field in the photo so 140 IRE jump?). When the beam does this, it shoots past the IRE level desired and then oscillates for a spell. That's what makes those waves in the picture.
If you are using a VP or HTPC you can do as others suggest and increase your porch sizes, to make the raster bigger, to allow for even further positioning of the image away from the edge. However, keep in mind that when you increase the pixel count you also draw more bandwidth and your image may become softer.
The G90 is the best projector in terms of being able to make this distortion almost invisible, but you can still see it if you know what to look for.
craigr |
Thanks for the very detailed explanation, Craig. Between shifting the raster to the far left and compensating via a VP/HTPC, which of the two methods do you prefer? You listed one con of the VP method being a potentially softer image. Are there any cons to shifting the raster? Would that give you uneven wear? |
There really isn't any harm in shifting the image to one side of the raster or the other. Wear results from the projected image, not the raster. Your image should still be centered on the tube, but with the raster off center...
...which does raise a small risk with this method. If you have the raster off center and project an image initially, you may find that the image goes off the edge of the tube face. You should be mindful of this initial situation and be ready to recenter your image quickly so it's not sitting there running off the tube face. But once that's done you should be good to go.
When I set up 1080p on a projector, I always try and keep the image as far away from the leading edge of the raster as possible (on almost every projector model). I leave HTPC's to my customers, so if they know how to adjust porches that's their prerogative. I will sometimes adjust the timings on a VP if I have one at my disposal for a particular job. So I suggest at least off centering the image and possibly also using the video timings to your advantage.
One other thing, you may find that as you move the image closer to the trailing edge of the raster that the trailing edge of the image will suddenly become nonlinear geometrically. The easiest way to detect this is to have a cross hatch up while you make adjustments and watch the dimensions of the squares to the right of the screen (when facing the screen). If you see the far right column start to get thinner than the other columns than you have gone too far  THat type of linearity error can not be corrected with geometry controls.
craigr
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CIR Engineering
Joined: 25 Aug 2008
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Location: Chicago USA & Berlin Germany
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| Posted: Mon Feb 23, 2009 1:39 pm Post subject: |
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| Quote: |
You make it sound like a video chain issue Craig. Overshoot in the neckboards.
It's my understanding that it is a beam settling issue. The beam is oscillating: faster = dimmer, slower = brighter.
If it was neckboards it would happen anyway, not just on the LH edge.
Mark |
Sorry for any confusion. I know that over-shoot often is in reference to intentional (or unintentional) manipulation of the video path which accentuates high frequencies... which usually leads to ringing especially when it's over done http://www.cir-engineering.com/white_papers/pcbmod/PCBmod.htm.
This distortion takes place in the tube, not the video chain (though I haven't put a scope on a VNB for a while to check both). I've also heard of this distortion referred to as settling too.
craigr
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Last edited by CIR Engineering on Mon Feb 23, 2009 1:59 pm; edited 1 time in total
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Nashou66
Joined: 12 Jan 2007
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Location: West Seneca NY
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Mon Feb 23, 2009 2:00 pm Post subject: |
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| Nashou66 wrote: | Craig you explanation is correct as I remember Scott from VDC explaining how the retrace and settling times of the beam work to me once in a PM for a Vim issue I had. marquees need 1us or longer sync timings to be happy, the closer to 1us they ger weird things can happen.
Athanasios |
Yeah, I think this is all a function of the tube and not at all in the video chain. Makes me want to go back and double check though.
Either way, you can reduce or eliminate the distortion by getting the image away from the leading edge of the raster regardless of where the distortion originates. As long as the image is past the ripple you can't see it.
craigr
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schmoe
Joined: 30 Mar 2008
Posts: 374
Location: Seattle, WA
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| Posted: Mon Feb 23, 2009 5:12 pm Post subject: |
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| CIR Engineering wrote: | There really isn't any harm in shifting the image to one side of the raster or the other. Wear results from the projected image, not the raster. Your image should still be centered on the tube, but with the raster off center...
...which does raise a small risk with this method. If you have the raster off center and project an image initially, you may find that the image goes off the edge of the tube face. You should be mindful of this initial situation and be ready to recenter your image quickly so it's not sitting there running off the tube face. But once that's done you should be good to go.
When I set up 1080p on a projector, I always try and keep the image as far away from the leading edge of the raster as possible (on almost every projector model). I leave HTPC's to my customers, so if they know how to adjust porches that's their prerogative. I will sometimes adjust the timings on a VP if I have one at my disposal for a particular job. So I suggest at least off centering the image and possibly also using the video timings to your advantage.
One other thing, you may find that as you move the image closer to the trailing edge of the raster that the trailing edge of the image will suddenly become nonlinear geometrically. The easiest way to detect this is to have a cross hatch up while you make adjustments and watch the dimensions of the squares to the right of the screen (when facing the screen). If you see the far right column start to get thinner than the other columns than you have gone too far THat type of linearity error can not be corrected with geometry controls. |
Thanks again for the helpful explanations. I don't own a VP that allows me to modify porch settings so I'm glad to hear there's another workaround. I will try the raster shift soon and let you all know how it went.
Btw, would any of the devices sold on this site (Buf2000, GammaX, RTC2200, etc.) have any controls that would help get rid of the ringing? Probably a dumb question but I have to buy something that let's me control gamma anyway, so I thought it wouldn't hurt to ask. 
Thanks again.
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Wed Feb 25, 2009 12:15 am Post subject: |
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More porch pixels/reduced width will mean that you may have to more the projector back...closer to the factory settings...to fill the screen.
If I want to eliminate the ringing on my XG at 1080i 96hz I really need to move the projector back.
I think that is what I was trying to say 
How come when you say it, it doesn't get stuffed up your a$$? 
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Mark_A_W
Joined: 15 Mar 2006
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Location: Sunny Melbourne Australia
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| Posted: Wed Feb 25, 2009 1:49 am Post subject: |
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Coz I type in an Or-strayl-yan accent....mate
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schmoe
Joined: 30 Mar 2008
Posts: 374
Location: Seattle, WA
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| Posted: Wed Feb 25, 2009 4:19 am Post subject: |
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Sorry guys, but I'm having a total n00b moment here. I'm confused by the interactions between raster size/position and image size/position.
I can use the Phase setting to shift the image horizontally away from the edge of the raster. However, when I do that almost immediately the other edge of the image is cut off by running off the end of the raster. How do I counteract this? If I use the Size setting, it appears to adjust the size of the raster and not the image, therefore I can't figure out how to shrink the image to bring the cutoff bit back into view.
Am I using the wrong controls? How do I change the raster size independently of the image size?
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Nashou66
Joined: 12 Jan 2007
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Location: West Seneca NY
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schmoe
Joined: 30 Mar 2008
Posts: 374
Location: Seattle, WA
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| Posted: Wed Feb 25, 2009 5:34 am Post subject: |
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Unless you're talking about a different setup, the Guided Mechanical Setup (Help -> 2) only lets you center the raster, as far as I can tell. I don't see anything for enlarging the raster.
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Mark_A_W
Joined: 15 Mar 2006
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Location: Sunny Melbourne Australia
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| Posted: Wed Feb 25, 2009 6:03 am Post subject: |
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| schmoe wrote: | | How do I change the raster size independently of the image size? |
By changing the porch pixels in the source. The projector cannot do this.
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schmoe
Joined: 30 Mar 2008
Posts: 374
Location: Seattle, WA
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| Posted: Wed Feb 25, 2009 6:08 am Post subject: |
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ugh. OK, so earlier in this thread we determined there are two ways to get rid of the jail bar banding:
1. Changing porch settings via HTPC or VP.
2. Shift the raster to the left and center the image within the tube face (with the raster off-center)
I'm trying to figure out how to accomplish #2. I can shift the raster, but I can't change it's size. So if I try shifting the image then a large portion of the image will get cut off. Unless I'm missing something, it doesn't look like #2 is possible. 
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Wed Feb 25, 2009 10:39 am Post subject: |
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| schmoe wrote: | ugh. OK, so earlier in this thread we determined there are two ways to get rid of the jail bar banding:
1. Changing porch settings via HTPC or VP.
2. Shift the raster to the left and center the image within the tube face (with the raster off-center)
I'm trying to figure out how to accomplish #2. I can shift the raster, but I can't change it's size. So if I try shifting the image then a large portion of the image will get cut off. Unless I'm missing something, it doesn't look like #2 is possible. |
Changing the image size in the raster IS no 1.
But without that you still should be able to shift the raster and the image separately...unless you own a Sony. You certainly can with a NEC (Raster Centering and Image Position).
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tse
Joined: 03 May 2006
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Location: Sweatbucket, Fl.
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| Posted: Wed Feb 25, 2009 1:28 pm Post subject: |
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Only the long/short retrace setting will change the image size relative to the raster size as far as the projector is concerned. Short retrace should give alot of extra raster so the image can be phased over.
Scott
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Wed Feb 25, 2009 3:54 pm Post subject: |
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| tse wrote: | Only the long/short retrace setting will change the image size relative to the raster size as far as the projector is concerned. Short retrace should give alot of extra raster so the image can be phased over.
Scott |
Exactly.
With a 9500 you will also most likely wind up with the width control maxed (or almost maxed) out. This is a difficult set of adjustments on a Marquee, but it can be done. You also can play with the magnets to move around the raster and image together...
craigr
_________________
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CIR Engineering
Joined: 25 Aug 2008
Posts: 4269
Location: Chicago USA & Berlin Germany
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| Posted: Wed Feb 25, 2009 3:57 pm Post subject: |
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| Mark_A_W wrote: |
But without that you still should be able to shift the raster and the image separately...unless you own a Sony. You certainly can with a NEC (Raster Centering and Image Position). |
What Sony are you talking about... this can be done with both the G90 and G70 projectors. You use "Shift" to move the image and raster together, and you use "Cent" to move the the image inside the raster... actually a lot of folks don't seem to get this technique as I have seen it misunderstood all the time.
craigr
_________________
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Murideo Fresco SIX-A HDMI 2.x Analyzer
Light Illusion ColourSpace XPT Color Calibration Software
Light Illusion LightSpace XPT Pro Version 10.x Color Calibration Software
OMARDRIS JVC Software Patch to use K10-A and Jeti with JVC OEM AutoCal Software!
Sencore CR7000 CRT Tube Analyzer / Rejuvenater
Authorized Dealer for Lumagen & just about everything worth buying
www.CIR-Engineering.com - craigr@cir-engineering.com
Phone: 865-405-6892
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Wed Feb 25, 2009 10:37 pm Post subject: |
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Sorry, my mistake, my memory deceived me.
It's the Test Patterns we couldn't centre.
I still think there's something really funky about setting up a G series Sony - we just couldn't get everything where we wanted it it (Raster, Image and Test Patterns).
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