Complex Horizontal Disortion on the Top Edge

Hello Fellowers,

after weeks of testing and playing around with the placement of my PPM I have to involve you.

What is the reason that the top Edge of the picture has such a weird pixel disortion?

(With regards to the bottom disortion “I am fine”, because the screen and the PPM have not a 100% horizontal calibration)


I think your PPM isn’t at the center of the screen so it is angled a bit making one side of the screen taller than the other side.

But is this relevant for the waves on the Top Edge?

P.S. The PPM is more or less in the center of the projection screen:


Never challenge a German :sunglasses: he would have measured everything before posting. I would have and I’m just Austrian.:joy:


Could it be distortion in your PJ screen? Mine isn’t perfect either (a different projector) Have you tried the same test and measurements but on a flat wall for comparison?

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First of all:
@SchmuFoo :clap:t4: :raised_hands:t4: for being so thourough, I really like your approach! :sunglasses::+1:t4:

@Sponnie has the correct answer in my opinion. The lens could created something like this also, but I think it’s surface tension in your screen leading to the screen not being completely flat at that spot.
See if you can find a (white) furniture plank and hold that in front of the image at that point? Or try projecting onto a white door. :bulb:


I am pretty sure the projection surface (the screen) is wavy.

Please shine the laser from an edge of the screen and check if it’s perfectly straight or not.


I see. I didn’t notice the wave :sweat_smile: But yeah, like what they said, it’s most likely caused by your screen. It’s not tensioned? Also, I assume you don’t use any of the digital corrections. In my observation, they do cause some jagged edged/corners but not waves.

As said, your screen should be wavy. That makes funny effects when a car is in profile on the screen.
In this state, I only found a crossbar (wooden or aluminum) to put in place (at the back of the projector) to solve part of the problem. But in your case, I don’t have the impression that the image is as distorted as that.

Guys have a look at the top and bottom part of his image projection. They are nearly dead straight. Only the inside part from the startup page is wavy so the assumption that his screen is wavy is wrong.

Are they though, or is it the black line from the screen obscuring the wavy edge of light making the image look straight and sharp even when it’s not?

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Hmmmm ? Only SchmuFoo can answer that. But he hasn’t come back here yet