Your post needs to be edited if you want it to address the same conditions as the thread title.
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Is half a pixel of misconvergence worse, better, or equal to half a pixel of chromatic aberration?
If you have two projectors totally equal in every way, except one has zero misconvergence, and half a pixel of chromatic aberration, while the other has zero chromatic aberration, but zero misconvergence, will these projectors still perform totally equal, or, from viewing distance, will one of these be more visible, or soften the image more, than the other?
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If you can digitally correct them both, then they are the same. If you can only digitally correct convergence, then misconvergence is better.
OTOH, if the chromatic aberration is only present on the edges, that's not too bad. Then I might lean the other way, since it would be mostly pixel sharp.
OTOH, if the chromatic aberration is only present on the edges, that's not too bad. Then I might lean the other way, since it would be mostly pixel sharp.
Thanks for the heads up, but I'm unclear what you mean.Your post needs to be edited if you want it to address the same conditions as the thread title.
Assuming both are in the same place, one one each projector, and both are uncorrectable?If you can digitally correct them both, then they are the same. If you can only digitally correct convergence, then misconvergence is better.
OTOH, if the chromatic aberration is only present on the edges, that's not too bad. Then I might lean the other way, since it would be mostly pixel sharp.
Basically the question is, is one of the two less part of the image than the other? Would half a pixel of misconvergence affect the clarity of the image, from 5 feet away, by 5%, but half a pixel of aberration would only affect the clarity of the image, from 5 feet away, by 2.5%, or would both affect 5%?
If you have a half pixel red line on your screen that's not supposed to be there, from viewing distance does it matter what is causing it, because either way it is a red line, or is one somehow more transparent, or less problematic to the image, than the other? That's my question.
If red is off from green, it's off. Doesn't matter what caused it. If blue is off from green, that matters less than red. Still doesn't matter what caused it, other than doing geometric correction. Half pixel geometric correction ads a small amount of blurriness to that color. Green is the most important, since we're most sensitive to green.Assuming both are in the same place, one one each projector, and both are uncorrectable?
Basically the question is, is one of the two less part of the image than the other? Would half a pixel of misconvergence affect the clarity of the image, from 5 feet away, by 5%, but half a pixel of aberration would only affect the clarity of the image, from 5 feet away, by 2.5%, or would both affect 5%?
If you have a half pixel red line on your screen that's not supposed to be there, from viewing distance does it matter what is causing it, because either way it is a red line, or is one somehow more transparent, or less problematic to the image, than the other? That's my question.
Interesting. Others have said we are most sensitive to red. Either way, this is what I mean. In a DLP projector for example, the light shines onto the mirrors that make the pixels, then the mirrors reflect the light out of the lens. So wherever the pixels are on the mirror device, you will get the full light from that pixel. Whereas chromatic aberration seems to be a situation where the light shines out the lens, but then there is an imperfection in the lens, so some of the light angles off over the screen screen somewhere it's supposed to.If red is off from green, it's off. Doesn't matter what caused it. If blue is off from green, that matters less than red. Still doesn't matter what caused it, other than doing geometric correction. Half pixel geometric correction ads a small amount of blurriness to that color. Green is the most important, since we're most sensitive to green.
But is this the full light from the pixel, or only for example half of the light's wavelengths, that are affected by the lens imperfections, while the other half would not affected? In a case like that, maybe misconvergence would be worse than chromatic aberration because with misconvergence, you're getting the full red, green, or blue light from the projector going to the wrong place, concentrated in the wrong place, whereas with chromatic aberration, it could just be the lens spreading out part of the red, green, or blue light from the projector to the wrong place, but not all of it.
I don't know if it works like that, but that is what I was asking about. At first glance, of course, half of red off is half of red off, who cares what caused it. But maybe it actually does matter what causes it. I have a projector that cannot have misconvergence, but it has a little chromatic aberration, and some of it does like more "faded" than misconvergence I've seen in the past. It seems not as concentrated. If you imagine a drawing of a red line on a piece of paper, the chromatic aberration looks more like if you shaded some extra red shadow on the side of the crisp line, whereas, again I dont know for sure, but maybe misconvergence would be more like the entire crisp line is in the wrong place, where the shadow would be.
With misconvergence, we know that the half pixel that is misconverged is missing from the place it's supposed to be, and showing up in a place it's not supposed to be. But with chromatic aberration, is the lens aberrating the light from where it's supposed to be to somewhere it's not supposed to be, or is the light still going where it's supposed to be, but now the lens is spreading it out further and also sending it where it's not supposed to be? Whereas with misconvergence, it would probably be both missing from the correct spot and in the wrong spot.
But again, maybe for chromatic aberration to show a half pixel where it's not supposed to be, it will mean it is also missing from where it should be. But say it'sa green pixel, maybe only half the green wavelengths are affected by chromatic aberration, so then at least you still have half of green in the place its supposed to be, instead of none, and the other half off to the side. See what I mean? So that is what we need to figure out, then we can leave the thread to the search archives for anyone else who wants to learn about this.
Here are the perceptual contributions from red, green, and blue:Interesting. Others have said we are most sensitive to red. Either way, this is what I mean. In a DLP projector for example, the light shines onto the mirrors that make the pixels, then the mirrors reflect the light out of the lens. So wherever the pixels are on the mirror device, you will get the full light from that pixel. Whereas chromatic aberration seems to be a situation where the light shines out the lens, but then there is an imperfection in the lens, so some of the light angles off over the screen screen somewhere it's supposed to.
But is this the full light from the pixel, or only for example half of the light's wavelengths, that are affected by the lens imperfections, while the other half would not affected? In a case like that, maybe misconvergence would be worse than chromatic aberration because with misconvergence, you're getting the full red, green, or blue light from the projector going to the wrong place, concentrated in the wrong place, whereas with chromatic aberration, it could just be the lens spreading out part of the red, green, or blue light from the projector to the wrong place, but not all of it.
I don't know if it works like that, but that is what I was asking about. At first glance, of course, half of red off is half of red off, who cares what caused it. But maybe it actually does matter what causes it. I have a projector that cannot have misconvergence, but it has a little chromatic aberration, and some of it does like more "faded" than misconvergence I've seen in the past. It seems not as concentrated. If you imagine a drawing of a red line on a piece of paper, the chromatic aberration looks more like if you shaded some extra red shadow on the side of the crisp line, whereas, again I dont know for sure, but maybe misconvergence would be more like the entire crisp line is in the wrong place, where the shadow would be.
With misconvergence, we know that the half pixel that is misconverged is missing from the place it's supposed to be, and showing up in a place it's not supposed to be. But with chromatic aberration, is the lens aberrating the light from where it's supposed to be to somewhere it's not supposed to be, or is the light still going where it's supposed to be, but now the lens is spreading it out further and also sending it where it's not supposed to be? Whereas with misconvergence, it would probably be both missing from the correct spot and in the wrong spot.
But again, maybe for chromatic aberration to show a half pixel where it's not supposed to be, it will mean it is also missing from where it should be. But say it'sa green pixel, maybe only half the green wavelengths are affected by chromatic aberration, so then at least you still have half of green in the place its supposed to be, instead of none, and the other half off to the side. See what I mean? So that is what we need to figure out, then we can leave the thread to the search archives for anyone else who wants to learn about this.
0.299*R + 0.587*G + 0.114*B
So, you can see that green is most important and blue is least important.
When it comes to convergence and and CA, it's about lining up the red and blue with the green.
For a 3 chip display, where convergence is a problem, you can apply fractional pixel shifts to line them up perfectly.
The only downside to a fractional pixel shift is that you sacrifice some sharpness, because it has to blend neighboring pixels for a fractional shift.
You never shift green, and video typically has color at half resolution anyway, so it's not that bad.
On the other hand, DLP chips use pixel shift. They aren't native 4k resolution, so you are starting with half resolution, including the most critical green channel.
Overall, native 4k is sharper, but lens quality also plays a big role in 4k.
Chromatic aberration is typically sharp in the center, which is most important.
Also, digital correction works well for both of these problems, provided that the electronics supports it.
You'll still get the sharpest image from a good lens with edge to edge pixel sharpness.
I'm not quite sure what you mean by CA looking washed out. That might be CA, or it might be some other aspect of the projector's image quality (contrast, color space coverage, calibration.)
You are right about CA affecting different wavelengths partially. It depends on the light source whether each color has a narrow spectrum or a wide spectrum. This can limit how much digital correction can fix, but regardless, digital correction can have a major benefit.
Overall, the answer to this stuff always comes down to "it depends." You can't theoretically say that a projector is better or worse based on convergence vs CA. You need to know a lot more about the details.
Well if misconvergence moves all the light of a pixel, but CA only moves some of the light, it would seem like having only say 50% of the light being "off" would be better than having 100% of the light being "off." That's what I was wondering about. But I agree there are many factors involved.Overall, the answer to this stuff always comes down to "it depends." You can't theoretically say that a projector is better or worse based on convergence vs CA. You need to know a lot more about the details.
For convergence correction, whole pixel shifts can be done without any loss of sharpness. The worst case scenario is a half pixel shift of red and a half pixel shift of blue. (Green never gets shifted.)Well if misconvergence moves all the light of a pixel, but CA only moves some of the light, it would seem like having only say 50% of the light being "off" would be better than having 100% of the light being "off." That's what I was wondering about. But I agree there are many factors involved.
Keep in mind that the best case scenario of DLP is almost as sharp as the worst case for 3 misconverged native 4k chips.
All this stuff is pretty theoretical, assuming good lenses. Full 4k resolution is past the limits visual acuity for typical screen sizes.
Better to worry about lenses, brightness, contrast, color, HDR, etc.
Better to worry about lenses, brightness, contrast, color, HDR, etc.
If the panels are not converged or there is chromatic Aberrations, panel alignment via convergence is necessary. Period.
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