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Discussion Starter · #1 ·
I'm currently in an apartment and the room layout is not ideal for a projector system. Which current unit has the best keystone correction? The unit will receive DVD only as I currently have no HD sources, so a good internal scaler would be nice, too...Thanks.


Jason
 

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Why do you need keystone correction? How is the room so bad to need keystoning?
 

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none of them are good. they all trash the image. HOWEVER... depending on how critical your eye is, you may not even notice. I personally would never use it.
 

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Discussion Starter · #4 ·
I would personally never want to use it, but due to a poorly placed ceiling fan, the only way I can have a projector is to use keystone correction, unless i want a 65" diag. picture. I'm thinking along the lines of having a less than ideal set-up now knowing it would improve later when my living situation improves. And I can't move the fan, I've already asked.
 

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Don't believe all the hype. Digital keystone correction is not as bad as everyone makes it out to be on this forum. Before buying my projector (Sharp Z10000), I swore against using digital keystone correction, and I even built a custom drop platform just so I wouldn't have to use it. Well after finishing this very extensive project and getting the projector hung, I decided to compare the lowered projector image with no keystone correction vs. the raised projector image with keystone correction. In the raised position the projector is over 2 feet above the top of the screen at 16 feet back, which requires a keystone setting of 20. This is pretty significant. The result - I wasted 5 days of work building the drop platform. I cannot tell a difference between the corrected and non-corrected image when watching either DVDs or HDTV at any viewing distance. The only time I can tell a difference is when using my HTPC for regular Windows stuff. The text gets a bit garbled on small, thin fonts. Fonts with line widths greater than 1 pixel, however, still look very good. I don't even bother using my drop platform anymore. I just leave the projector in the raised position all the time now.


It may be that the Sharp does an excellent job here over other projectors, and employs a very good anti-aliasing algorithm. I have seen other projectors with keystone correction being used that didn't look so good.


I am losing about 20 lines or vertical resolution, but like I said, I can't tell the difference.


Chris


p.s. It sounds like in your situation you need the projector to be within the screen area. The Sharp does this without keystone correction as do some others, by using the lens shift feature. The Z10000 can be placed anywhere between the top and bottom of the screen in either regular or inverted position, but it does need to be centered horizontally.
 

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Discussion Starter · #7 ·
I can't center it horizontally...If I went with a 16:9 106" diag. screen, the projector would have to be at the right edge of the screen. The only way I could center it horizontally is to coffee table mount it. Vertically, I have some room to play, but not much. I currently have a Mits. 55" HDTV that I'm looking to upgrade from. I may wait...
 

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Oh. Ouch. Most projectors do not do horizontal keystone correction, and require a horizontally centered projector. I remember reading on this forum about one of the new HD2 projectors that could do horizontal lens shifting without using digital keystone correction, but I cannot remember which projector it was. At the large offset angle you are talking about, you are probably going to see significant picture degradation with digital keystone correction if you can find a projector that even does it horizontally. I'm at about 9 degrees vertical, and I don't think I would want to go much more than that. Your angle would be much larger if you are placing the projector at the far right edge depending on how far back you are projecting from. A projector with horizontal lens offset would be the best bet in your case. Maybe someone else remembers which model it is that can do this. If I can find the thread, I'll repost.


Also - projecting from that kind of angle will limit your screen choices. You probably wouldn't want to get a Firehawk in this case as you'll lose a lot of brightness.


Chris
 

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JMPyle, How about either a short or long throw projector? You could ceiling mount something like a Marantz in front of the fan or a Sharp or JVC DILA behind the fan. Or go with a rear projection setup bouncing the image off a mirror. If you really NEED horizontal keystoning, the Sharp Z90 (not the Z9000) supposedly does a really good job at horizontal keystoning.
 

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Don't believe the hyperbole that the digital keystoning has to ruin the image. I bought into this belief until I actually tried it for myself on my NEC HT1000. The truth is that it's very hard to detect on moving video - even HiDef. Of course the ideal situation is to avoid it. But if this isn't possible then digital keystone correction is a viable alternative. I can't speak for other projectors but the NEC HT1000 has both horizontal and vertical keystoning and it does a superb job of it.


-Dylan
 

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Discussion Starter · #11 ·
I can't do rear projection due to screen location or long throw, which would still have issues with the ceiling fan. Realistically, I cannot do a ceiling mount. Landlord won't let me mount it to the ceiling. A short throw would be a good option if I could table mount it...any thoughts?
 

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Chris Sander


You state:

"I am losing about 20 lines or vertical resolution, but like I said, I can't tell the difference. "


Do you mean that the keystone correction reduces the vertical height of the image? Doesn't this change your aspect ratio or does the correction also change horizontal resolution by an equal amount?


Thanks

Bob
 

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In order for keystone correction to work, you have to give up some horizontal lines of resolution. The reason for this might not be completely obvious at first, but it will be when you try it out. I'll try to explain. If you are tilting the projector downward, keystone correction has to reduce the width of the bottom of the picture by chopping off some pixels on each side in order to correct the geometry. Now that you have that done, you'll have to zoom the projector in a bit more so that the width of the screen is again filled from top to bottom. Some of the pixels are now displaying off the screen, but these are the ones darkened by the correction. Now if keystone correction didn't reduce the number of horizontal lines, some of the picture would be displaying off the bottom (or top) of the screen.


So keystone correction shortens some of the horizontal lines (to fix the geometry), and chops off some of the other horizontal lines (to preserve the aspect ratio). I think you lose more pixels to the aspect ratio part of keystone correction than you do to the geometry part of it.


Chris
 

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Chris


"So keystone correction shortens some of the horizontal lines (to fix the geometry), and chops off some of the other horizontal lines (to preserve the aspect ratio). I think you lose more pixels to the aspect ratio part of keystone correction than you do to the geometry part of it. "


Now I see how this affects resolution as such. The image actually would not change as you can use the zoom to get the image size back to original as aspect ratio is preserved. I suppose less resolution is why there is a "softer" picture as stated on a number of posts on keystone correction.


Thanks for answering my question.


Bob
 
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