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Discussion Starter · #1 ·
Hi all,

I'm trying to diagnose some convergence issues on an old JVC projector, and wondering if anyone has seem similar problems.

I'm using a 4k pattern with single pixel` dots made of red and green.

If I align the green and red panels by looking at the middle of the screen, off to the right of the screen green is off by what seems like an absurd amount. It's also smeared to be a few times the normal pixel width.

Anyone know what could be causing this smearing?

Anything to be done here or does this projector belong in the trash heap?
 

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I would zero out zonal convergence controls on all three panels and use only whole screen convergence to see if this is a being induced by the zone convergence system.
 

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Hi all,

I'm trying to diagnose some convergence issues on an old JVC projector, and wondering if anyone has seem similar problems.

I'm using a 4k pattern with single pixel` dots made of red and green.

If I align the green and red panels by looking at the middle of the screen, off to the right of the screen green is off by what seems like an absurd amount. It's also smeared to be a few times the normal pixel width.

Anyone know what could be causing this smearing?

Anything to be done here or does this projector belong in the trash heap?
What projector is this? You said "on an old JVC" but the only 4K capable JVCs aren't old. For "older JVC projectors", you should have e-shift disabled and do all your focus and aligning in the 1080p space.

That being said, it's not uncommon to have the sides be out of convergence with the center. The general consensus is to align for the center using full pixel adjustments only and live with the sides being out. But if you see the misconvergence from your seating, you can use zone fine convergence and adjust out the sides by doing each zone separately. If you copy your lens memory and keep one converged via zone and one not, you can quickly switch between the two and see what you like better. Remember you have 3 panels but can align 2 the 3rd stays in place. So green means both blue and red is out. If you have too much green to the right, red and blue need to move to the right. If you see too much red or blue, just that one color needs to move.
 

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Discussion Starter · #4 ·
What projector is this? You said "on an old JVC" but the only 4K capable JVCs aren't old. For "older JVC projectors", you should have e-shift disabled and do all your focus and aligning in the 1080p space.

That being said, it's not uncommon to have the sides be out of convergence with the center. The general consensus is to align for the center using full pixel adjustments only and live with the sides being out. But if you see the misconvergence from your seating, you can use zone fine convergence and adjust out the sides by doing each zone separately. If you copy your lens memory and keep one converged via zone and one not, you can quickly switch between the two and see what you like better. Remember you have 3 panels but can align 2 the 3rd stays in place. So green means both blue and red is out. If you have too much green to the right, red and blue need to move to the right. If you see too much red or blue, just that one color needs to move.
I would zero out zonal convergence controls on all three panels and use only whole screen convergence to see if this is a being induced by the zone convergence system.
It's a simulation projector - 4096 x 2400 native. I think this unit is probably 10 years old at this point. Sadly has no zone adjustment, though I'm looking into MPC HC filters to do that in software to see if it helps.

The issue that confuses me here is the horizontal smearing of the green pixels. This is only happening on the right hand side of the image, and only to green. Any idea if this is some panel problem or if something is messed with the optics? If you zoom up close on the "right.jpg" above you'll see what I mean.

Also very curious how bad you would rate this convergence relative to an average LCOS unit (before zonal convergence)? I feel like you've seen a lot more units than I have.
 

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It's a simulation projector - 4096 x 2400 native. I think this unit is probably 10 years old at this point. Sadly has no zone adjustment, though I'm looking into MPC HC filters to do that in software to see if it helps.

The issue that confuses me here is the horizontal smearing of the green pixels. This is only happening on the right hand side of the image, and only to green. Any idea if this is some panel problem or if something is messed with the optics? If you zoom up close on the "right.jpg" above you'll see what I mean.

Also very curious how bad you would rate this convergence relative to an average LCOS unit (before zonal convergence)? I feel like you've seen a lot more units than I have.
It seems pretty bad. The green just means both the red and blue are missing on those green areas. If you move both red and blue over a notch, that green probably goes away (and some other problem happens elsewhere). Most likely your only solution is to fix it in the middle of your screen and live with it. How bad is it when you're in your regular seats just using the projector? How far away do you sit from what sized screen?
 

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Discussion Starter · #6 ·
It seems pretty bad. The green just means both the red and blue are missing on those green areas. If you move both red and blue over a notch, that green probably goes away (and some other problem happens elsewhere). Most likely your only solution is to fix it in the middle of your screen and live with it. How bad is it when you're in your regular seats just using the projector? How far away do you sit from what sized screen?
There's actually no blue in this pattern, it's just Green + Red. But yeah, I get the convergence problem on the right. I just don't get the additional horizontal smearing - as if the green alone is out of focus and only on the right side of the panel.

As in, if it were just a convergence problem I would just expect to see well defined and separate green and red dots in this area on this pattern.

I'm 10 ft back from a 13 ft wide scope screen. I haven't mounted it in a way I can fill the screen yet, but will try it sitting a proportional distance back.
 

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There's actually no blue in this pattern, it's just Green + Red. But yeah, I get the convergence problem on the right. I just don't get the additional horizontal smearing - as if the green alone is out of focus and only on the right side of the panel.

As in, if it were just a convergence problem I would just expect to see well defined and separate green and red dots in this area on this pattern.

I'm 10 ft back from a 13 ft wide scope screen. I haven't mounted it in a way I can fill the screen yet, but will try it sitting a proportional distance back.
There is always blue, red, and green. When those elements are in alignment you get white. If you don't see blue but you see red and green, that means the red is out of alignment and the green is out of alignment. But green cannot be out of alignment. For green to be out of alignment it means both blue and red are out of alignment. So if you have red on the left and green on the right of a white element, the fix is move blue to the right one, red to the right 2. Moving blue to the right 1 will help the green (it will look like whatever blue plus green is) and adding the red will make it white.

Moving both red and blue to the left one is equivalent to moving green to the right one.

10 feet back from 13 feet wide sounds exactly perfect for where I'd sit on that screen size. And at that distance I'd also be able to see the difference.
Your only option here may be zone alignment, but you're saying that doesn't exist in the simulation firmware? If so, you're sort of screwed and can only do what you can. I'd move both red and blue over to the right one and see how it looks at the center. I'd not sacrifice the center for the left side of the screen, though.

Do you have fine level alignment? It's possible you can get away with a half pixel move to the right and still be ok in the center. That takes a way a little resolution. You may not notice though.
 
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Discussion Starter · #8 ·
There is always blue, red, and green. When those elements are in alignment you get white. If you don't see blue but you see red and green, that means the red is out of alignment and the green is out of alignment. But green cannot be out of alignment. For green to be out of alignment it means both blue and red are out of alignment. So if you have red on the left and green on the right of a white element, the fix is move blue to the right one, red to the right 2. Moving blue to the right 1 will help the green (it will look like whatever blue plus green is) and adding the red will make it white.

Moving both red and blue to the left one is equivalent to moving green to the right one.

10 feet back from 13 feet wide sounds exactly perfect for where I'd sit on that screen size. And at that distance I'd also be able to see the difference.
Your only option here may be zone alignment, but you're saying that doesn't exist in the simulation firmware? If so, you're sort of screwed and can only do what you can. I'd move both red and blue over to the right one and see how it looks at the center. I'd not sacrifice the center for the left side of the screen, though.

Do you have fine level alignment? It's possible you can get away with a half pixel move to the right and still be ok in the center. That takes a way a little resolution. You may not notice though.
Ah I think I still didn't explain myself well. The pattern I photographed above is specifically made to have zero luminance in blue. It's a specific pattern I'm looking at that only has luminance in red and green channels. It's not a built in pattern of the projector.

Anyway, thanks very much for the feedback. I could do zone adjustment on my HTPC but it will take some time to learn the ropes, and of course I will lose sharpness from that I guess.

There is 1/10th pixel adjustment built into the projector so I'll give your last idea a shot too.

I'm curious if this local mis-convergence is a problem on 3DLP too? I know some of the nicer DLPs have physical adjustment knobs for the panels, but those couldn't correct a local problem like this. Are local convergence problems some deficiency of LCOS specifically?

I guess I don't even understand if the zone problems are due to inconsistency of pixel placement on the chips vs the chips being out of plane relative to the light path or something like that.
 

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Ah I think I still didn't explain myself well. The pattern I photographed above is specifically made to have zero luminance in blue. It's a specific pattern I'm looking at that only has luminance in red and green channels. It's not a built in pattern of the projector.

Anyway, thanks very much for the feedback. I could do zone adjustment on my HTPC but it will take some time to learn the ropes, and of course I will lose sharpness from that I guess.

There is 1/10th pixel adjustment built into the projector so I'll give your last idea a shot too.

I'm curious if this local mis-convergence is a problem on 3DLP too? I know some of the nicer DLPs have physical adjustment knobs for the panels, but those couldn't correct a local problem like this. Are local convergence problems some deficiency of LCOS specifically?

I guess I don't even understand if the zone problems are due to inconsistency of pixel placement on the chips vs the chips being out of plane relative to the light path or something like that.
So what's the projector's internal grid look like where you adjust convergence?
 

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Discussion Starter · #10 ·
Visual effect lighting Neon Electronic device Magenta Font
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It doesn't have a default pattern that comes up like in the RS/NX projectors. There's just a control interface over ethernet where you can make adjustments. It does have a few patterns built - there's a 3 color grid I pasted above where you can see the same red convergence issue (photo is again the right edge of the screen).

Also can see problems zooming up on the 4k QBF.

I presume on a new projector this amount of error would qualify for a replacement? Or would they just tell you to use the zone adjustments and keep it... :cautious:
 

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View attachment 3177378 View attachment 3177379

It doesn't have a default pattern that comes up like in the RS/NX projectors. There's just a control interface over ethernet where you can make adjustments. It does have a few patterns built - there's a 3 color grid I pasted above where you can see the same red convergence issue (photo is again the right edge of the screen).

Also can see problems zooming up on the 4k QBF.

I presume on a new projector this amount of error would qualify for a replacement? Or would they just tell you to use the zone adjustments and keep it... :cautious:
Do me a favor please just to humor me. Fire up the convergence screen or however you adjust that and adjust the red 2 to the left and the blue 1 to the left and snap the same photo of the QB Fox pattern (on the same segment of your screen)?

On a new projector, they'd tell you to use zone convergence yea. You'd be hearing "this is what Zone Convergence is for". If it was a flagship level projector like RS4500 you could probably super push and get something done - once. But if you got another sample with another issue they're not gonna keep replacing.
 

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Discussion Starter · #12 · (Edited)
Do me a favor please just to humor me. Fire up the convergence screen or however you adjust that and adjust the red 2 to the left and the blue 1 to the left and snap the same photo of the QB Fox pattern (on the same segment of your screen)?

On a new projector, they'd tell you to use zone convergence yea. You'd be hearing "this is what Zone Convergence is for". If it was a flagship level projector like RS4500 you could probably super push and get something done - once. But if you got another sample with another issue they're not gonna keep replacing.
Hey, I didn't mean to deprive you of the experiment but I already made some changes after I took that photo. I will post another QBF right here with current settings and happy to try any experiments from there :)

This is with a 3 pixel horizontal stretch in Red in MPC HC. That gives pretty decent alignment across the screen I think without having to do individual zones.

edit:
something was messed, will upload in a bit
 

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Discussion Starter · #14 ·
Do you have fine level alignment? It's possible you can get away with a half pixel move to the right and still be ok in the center. That takes a way a little resolution. You may not notice though.
I just found out from the description of this projector's sister model that the convergence adjustments on this are actually mechanical!

"Convergence adjustment function incorporated Color registration of RGB panels in the optical system can be mechanically adjusted in 1/4 and 1/10 pixel increments."

If this is true I'm pretty impressed- I've only heard of manually adjustable convergence on 3DLP before. Though it's sad they went through all this trouble and then didn't provide corrections for out of plane adjustment.
 
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