It's pretty easy to see if you are using a PC. Simply prepare a page of text with something like an 8pt bitmapped font (not a true type font.) With no keystone, it should be pixel-perfect. If you add keystone, the text on some parts of the screen starts to look pretty gnarly. Some letters are too thick and others too thin.
When evaluating various digital units during my recent search for a new projector, I encountered several with the digital keystone correction feature. Generally speaking, the picture was noticeably degraded with increased "stair-step" type artifacts when the feature was engaged.
I have not seen the LT150. However, I must say that the one projector I viewed which performed quite well with this feature engaged was the Plus UP-1080 (the unit on which the NEC LT150 is based). With all the other machines I tried, the digital keystone correction feature was not useable at all---it created more problems than it solved. With the UP-1080, I did see what I considered minor artifacts attributable to digital keystone correction, but these were much less apparent than with other machines.
Bob, could it be that the reason you're not noticing such artifacts with your LT150 is that they are being minimized by superior processing within this unit? Just a thought. Of course, as always, a particular user's individual sensitivities ultimately determine how much artifacting, if any, is acceptable.
It seems to me that, like onboard scaling, the digital keystone correction offered with various projectors is not necessarily equal in quality. If my limited experience (three weeks) with the UP-1080 suggests anything, Plus and NEC might be doing a better job of implementing digital keystone correction than some other manufacturers. I'm wondering if any LT150 owners have been able to compare how well this feature works in the LT150 versus other projectors.
It seems to be an almost universally held opinion that using the digital keystone correction found on some presentation projectors is to be avoided at all costs.
The LT150 is the first digital projector I've owned with this feature. I've been using it and so far I haven't noticed the artifacting which is supposed to result from this? What is it supposed to look like? And do other LT150 owners see it?
I have an LT150 connected to a Skyworth progressive dvd player thru component connection.
In cinema mode, the LT150 horizontally stretches the image to 1024 pixels (from 704 the dvd player puts out), and vertically stretches the image to 576 lines (from 480).
Now, in this scenario, the LT150 is already introducing scaling artifacts, though I haven't noticed them from my viewing position.
I would guess that digital keystone WOULD NOT introduce any more artifacts in this sort of setup, because the projector's scaling algorithms ought to be able to combine the two operations.
BUT, if you had an HTPC driving the LT150 at it's native resolution of 1024x768, then I think you would see some problems, because WinDVD would have scaled up to 1024x768, then the LT150 would be scaling it down, and wouldn't have any pixels to play with, since the full panel resolution was being used.
To repeat, if you need digital keystone in your LT150 installation, I bet that a GOOD progressive dvd player (not a bad one, mind you) would look better than an HTPC.
1. I do use digital keystone correction on my lt150 because it sits on my coffee table pointing up at the screen.
2. I think that an HTPC should look better than a progressive dvd player if there is NO keystone correction needed. But I haven't bothered because HTPC's are too much trouble for me. I tried it and didn't like the work necessary to operate a PC as a dvd player.
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