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Discussion Starter · #1 ·
Which of these two units has the least screendoor? The PLV-60 has a higher resolution & is 16:9 (so will use more of its pixels), but the XP21N has MLA, which may offset its lower resolution?


My theater has about 168" from screen to primary viewing area. I'm hoping to do a 120" diagonal 16:9 screen... is it possible to do that with either of these units without noticing the screendoor?
 

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Depending on your vision, at that distance to the screen you will not notice any screen door. However that is a very large screen. Think about using something a little smaller, say 103".
 

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MLA increases light output. Nobody has ever demonstrated this decreased the screen door effect, although ProjectorCentral thinks it does. However, ProjectorCentral has never done any side-by-side comparisions, so it is purely based on memory. At 13' with a 120" screen, screen door may be an issue. At 12' with a 96" screen, the XP21N looks outstanding, but at 10' screen door is an issue for me. You should be OK going over a little over 100".


For DVD's, in my opinion the added resolution of the PLV-60 doesn't really help, but should be a definite improvement with an HD input.
 

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Sitting at 16' from an 86" wide screen, screendoor is simply not an issue with my Boxlight 38T/Sanyo XP21N clone. I've played around with seating distance and concluded the rule of thumb of 2 times screen width really works for this projector.


Agree with Jonmx that no one has ever really proved less screendoor with MLA.


Dan
 

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I have done a side by side of both units. MLA DEFINITELY reduces screen door. I don't know how to prove it, since I don't have a digital camera, but my 12 year old saw it immediately. It was the first thing he mentioned. Side by side, or not, the differences are apparent from the same distance.


I sit at 15 feet from an 80" wide screen. No screen door on the 38t/21N. Even if I move up a couple of feet.


When I compared the two projectors, I set them at the same HEIGHT (60"), not width, because of the different shaped chip. That made a 110" wide, 125" diagonal picture. The sceen door doesn't go away until 16" on that size screen. It sounds like you only have 14 feet, which is closer than I sit for my 80" wide screen.


See my original post .



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Joe


"I'm a Dapper Dan man!"
 

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Great graphic Lenny! That make perfect sense. It explains why the grid lines look very similar to the grid lines on my LP350 DLP. The difference is negligible. You have to get to about a foot to see them closely.


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Joe


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Quote:
Agree with Jonmx that no one has ever really proved less screendoor with MLA.
See above posts by Lenny and Joe. That will teach me to make blanket statements! http://www.avsforum.com/ubb/biggrin.gif


(sound of Dan eating crow)


BTW, it sure looks like the MLA improves things, I just never had the opportunity to compare the two side by side like Joe has.


Have we ever figured out which of the new Sanyos have it and which don't?


Dan
 

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I have an XGA LCD projector -- Vidikron D-600 -- with a 120-inch diagonal screen. There's no MLA on this.


I watch from a distance of 22 feet and I see no screendoor effect at all. And I wear glasses that give me very good focus at that distance.
 

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Screen door really is all about getting the right screen size for the viewing distance.


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Joe


"I'm a Dapper Dan man!"
 

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You shouldn't see much, if any, screen door at 2.75 screen distance. Some prefer a wider field of vision (I'm sitting 1.2 screen widths away, that's one of the main reasons I added the ISCO II).


I've had LCD projectors since 92 and finally gave up on them because of the screen door, drove me nuts!


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John
My HT Picts
 

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Discussion Starter · #12 ·
Quote:
Originally posted by David Guill:
Depending on your vision, at that distance to the screen you will not notice any screen door. However that is a very large screen. Think about using something a little smaller, say 103".
A big part of why I'm planning to use a front projector instead of a rear-projection TV is for the larger image. Ideally I'm hoping for the same apparant image size (given distance to screen) as one experiences in a movie theater.


Given that there are 72" RP's on the market now, how big an advantage is there in a 86" FP?


I'd like to understand the limiting factors on size, and how to optimize...

- screendoor (which I'm now planning to see for myself & then try a Cygnus IMX lens to correct if necessary)

- resolution (the PLV-60 seems to have this covered)

- limitations in the quality of a DVD source (how effective are the "noise reduction" features of some DVD players, or of scalars, in improving this?)


Thanks for the great info, guys!
 

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John, one word... "MLA". (no, not "plastics")


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Joe


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Here are some pictures I did for a previous post. They are from my 10ht which uses the same panels as the pvl-60 so you can get some idea of the screen door. With a slight defocus you can achieve much of the benefit of a MLA. While I am sure MLA can do a better job at eliminating screendoor, from the pictures I have seen IMO it would not justify the additional expense of a 3rd party MLA lenses/image processor. I think the key thing to remember when focusing a digital projector, especially LCD, is you are trying to produce a clean focused overall image not a focused pixel.

Quote:
Originally posted by Jonmx:
MLA increases light output.


and


The only Sanyo I know for sure has the MLA is the XP21N, which adds about 25% more light output over the identical except for MLA XP18N unit.
I do not understand the claim that MLA will improve brightness. I do not understand how that can be possible as the lens can not produce more brightness than what is already produced by the bulb in the projector. I am not a lens expert or a light physicist but I would think that the brightness from a individual pixel would be lessened as the light is dissipated over a larger area to reduce the gap between pixels. It does not sound possible that you could take 2 projectors of equal lumen production, one with MLA and one without, placed at the same distance from a screen, projecting an identically sized image, and have the MLA one be brighter. Assuming that brighter means a higher lux meter reading at the screen. That would be a violation of The Law of Conservation of Energy. Jonmx, can you provide some supporting documentation for your statement. I see you are from IU country so it might be challenging to find some educated assistance, perhaps you can find a Boilermaker to help you out. http://www.avsforum.com/ubb/wink.gif (Hail Purdue!)


Screen door: Well I took a couple of pictures for you. I slightly defocus to mitigate screendoor. This does not affect sharpness at the macro level only at the sub pixel level


This is the best I can do with my camera it is fairly accurate in representing my screen door. This was taken using AVAI IRE 100 pattern. The color difference comes from the camera automatic adjustments with the yellow tape measure being placed in frame.

http://home.pacbell.net/btmoore/scrndoor_ruler.jpg

With ruler

http://home.pacbell.net/btmoore/scrndoor_noruler.jpg

No Ruler


Take this with salt as these digital cameras can not accurately demonstrate this as well as if you were looking at IRL.


Here is a picture of the sharpness pattern focused on the more detailed bars so you can see that the defocus does not affect picture quality or sharpness.
http://home.pacbell.net/btmoore/sharpness.jpg


Regards,


Brian


[This message has been edited by btmoore (edited 10-06-2001).]
 

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Quote:
Originally posted by btmoore:

I do not understand the claim that MLA will improve brightness. I do not understand how that can be possible as the lens can not produce more brightness than what is already produced by the bulb in the projector.

Its not a claim, but a fact. The XP18N and XP21N are identical except for MLA. The XP18N produces about 1800 lumens verses about 2400 lumens for the XP21N. If you look at Lenny's graphic you can see more of the light is focused through the LCD panel, so less light is loss with MLA. This focusing could very well reduce screen door effect. But the main reason MLA was invented was to increase the light output of the projector.
 

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Brian-

In regard to how identical projectors 1 with MLA and 1 without would have diferent light output at the screen I believe the Sanyo XP18N and the XP21N would be a case in point. These 2 projectors are reportedly identical except that the XP18N does not have MLA and the XP21N does. The lumen rating is 2000 for the XP18N and 2500 for the XP21N. The images I posted earlier in this post of MLA show light of the non MLA assembly being bounced back away from the screen while with the MLA assembly the beam is focused so there is no bounce back of light. This would seem to explain how the MLA achieves more light at the screen. I believe another example of this would be illustrated by the Dell marketed NEC LT154 which does not have MLA and produces 900 lumens and the identical NEC LT155 which has the MLA and produces 1200 lumens.
 

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leckian & Jonmx


What you are saying would make sense to me if a MLA was placed in front of each of the 3 LCD panels to pre focus light on to each individual LCD pixel. This would prevent light from being reflected or absorbed and thus conserved. Is this how the xp21N is constructed? Perhaps I am misinterpreting the Cygnus IMX processor as a MLA device, as this unit processes the light post passing through the LCD panles, in effect staggering pixels to mitigate fill factor issues. As I have never seen an MLA system I have been assuming that this what boxes like the xp21n are using. From your posts and now having a better contextual understanding of your graphic, it looks like these are 2 different technologies, one pre and one post processing. I can see no way a Cygnus IMX processor could improve brightness.


Regards,


Brian
 

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Yes, the IMX is an addon lens (I believe), while MLA works to focus the light through the LCD panel.
 

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From Lenny's graphic it looks like the individual MLA lenses focus a broad beam at the transparent part of the chip (pixel) so that ALL the light goes through the transparent part, rather than bouncing a percentage off the opaque grid between the transparent pixels. This would explain why the output through the chip increases, as there is less loss. Also, since it is focused and then spreads, it makes each pixel a little larger than it actually is on the screen, so they nearly meet, making the grid lines smaller at the screen, than they proportionately are at the chip.


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Joe


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Thanks Lenny for the graphic. I was unsure exactly what MLA was, but that makes it clear. The only Sanyo I know for sure has the MLA is the XP21N, which adds about 25% more light output over the identical except for MLA XP18N unit.
 
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