I plan to sit 1.2 screen widths away from the screen (for 2.35:1 movies, in a CIH setup).

Without going 1080p or AX100/AE900, it seems nothing else will save me from SDE.

What I don't understand is why slightly de-focussing the image can't work better than the AX100's smoothscreen technology.

In theory, if you use binoculars when de-focussing, and make sure the pixels become big enough to kill the gaps, but not too big to start overlap, the end result should be a picture without SDE at all, but also with no degradation in sharpness.

If theory can not be made practice in this issue, I would like to at least understand why.

I plan to sit 1.2 screen widths away from the screen (for 2.35:1 movies, in a CIH setup).

Without going 1080p or AX100/AE900, it seems nothing else will save me from SDE.

What I don't understand is why slightly de-focussing the image can't work better than the AX100's smoothscreen technology.

In theory, if you use binoculars when de-focussing, and make sure the pixels become big enough to kill the gaps, but not too big to start overlap, the end result should be a picture without SDE at all, but also with no degradation in sharpness.

If theory can not be made practice in this issue, I would like to at least understand why.

Well with smoothscreen, there is nothing you can do to adjust it. But with de-focusing at least you have options and you are in control.

Here is the answer I got from Caesar1, when I asked him about slightly de-focussing with his Epson 810, to get 1.2 screen widths image without SDE:

Yes, de-focusing works well. Small counter-clockwise turn from perfect focus, works for me. And I tested between 1.2 and 1.3 for that.

HD TV still looked real sharp (but perhaps a touch softer). I could not really tell a difference on standard DVDs. Psycologically it sort of bothers me (since I know my PJ is not in perfect focus), but I guess I can get over that.

There is a fine line though, between too much defocusing and just enough. You have to play with it.

2 questions:

1. Why does a counter-cockwise turn work better than clockwise ?. Does counter-clockwise turn, correlates to focussing the image slightly before the screen, or slightly after it ?, why does choosing one of these two is preferable to the other ?.

2. Why did HDTV look a tad less sharp after slightly de-focussing ?. The obvious answer is because you took it out of focus, but, if you read my first post again, you see that if you follow my instructions, then although you indeed took the pixels out of focus, you did not take the image out of focus, because there is no overlap between pixels.

Maybe the answer is that if you did it right, there was NO loss of sharpness in HDTV, rather the loss of SDE made it look like there is a loss in sharpness. But, if this is true, it still does not explain why you did not see a softer image with SDTV...

Hey Guys, you should put your locations in your profiles so they show up next to your names on posts - maybe someone close will offer for you to come see one of these in action...

I have thought about this some and have even tried it. What you are seeing in SDE is not the edge of the pixel but the dark line between pixels and it has width. When you are at sharp focus the width is the thinnest it can be. When you bump it off the dark line doesn’t go away its edges become fuzzy is all. The actual line is a fuzzy line that’s wider than before and the edged are blended. All it did when I tried it was give the image a poorer PQ IMO. The newer DLP are the way to go they keep making the transition line thinner and more neutral.

One thing not mentioned and once again this is IMO but texture on the screen has a way of lessening SDE for me. My DIY screen was made from canvas for that reason. The thread weave is very much like the texture some of the manufactured screens have. This issue of texture is debated all the time over in the DIY forum.

The newer DLP are the way to go they keep making the transition line thinner and more neutral.

I think the Panasonic AX100 is better than the newer DLP units in this regard.

Regarding your explanation, de-focussing superimposes the pixel with the black gaps around it. The superposition product is seen to be made just from the pixel, and not from the gaps, because the gaps are black, and the pixel is bright. So, the apparent black gaps do become thinner, and not just fuzzier.

I actually tried this morning and then viewed the results from about a foot away. I didn’t have time to take a before and after picture but I’ll try and do that later today or tomorrow and post the results. It shows up clearest on a test pattern but I’ll also do it on some movie content.

How much of a defocus do you thing is right in terms of pixel size?

How much of a defocus do you thing is right in terms of pixel size?
As much as you can, without making two adjacent pixels overlap, even not by a tiny bit.

There are images of test patterns that let you see if you can resolve full detail or not. Are you using such images ?.

As much as you can, without making two adjacent pixels overlap, even not by a tiny bit.

There are images of test patterns that let you see if you can resolve full detail or not. Are you using such images ?.

I've been using the one test pattern on the 810 PJ. Where do you get these other test patterns (are they on Avia)?

You should not use the test patterns on AVIA, because it only has SDTV patterns, which is low res, and so will not provide a good indication for the projector's sharpness under different de-focussing levels.

You need to check high res test patterns. You can find such patterns here:

http://www.w6rz.net/

Only problem is I can hardly find out 720p patterns, almost all of them are 1080p.

I've been told it is possible to generate a 720p pattern in Photoshop, but I don't know how.

Why do you need a special test pattern? Any image on the screen should be adequate as the focus and screen door is not dependant on what is being inputed. I would pick a bright image that SDE would be most noticable. I would recommend adjusting the focus the least amount possible to your taste from your closest seating position where the SDE is no longer noticable.

SDE cannot be completely wiped out. Shoot for a reduction rather than elimination. That is the only way it works effectively with a loss of focus. Put up a large b&w text and concentrate on the black against white back ground. Defocus as you pay attention to black.
Don't get it washed out. Just enough defocus to defuse the look of the grid without graying the color of black. It really gives a richer and smoother look and still details are there. This is only accomplished if you have a hi quality lens on your pj otherwise the result would be too much softening.