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Maybe I'm using the wrong terminology-the lense shift moves the picture up and down on the screen. By manually adjusting the projector up and down, you can vary the trapezoid and minimize or eliminate having to use the Keytone adjustment. According to other posts, the closer to zero the Keytone adjustment, the higher the resolution. How far off center your projector can be and still get an acceptable picture is beyond my expertise, but the closer to center the better. Think of shining a flashlight on a wall at an angle-one side of the beam will be brighter and smaller than the other. Side to side adjustments of the projector are totally manual, done by pivoting the projector on its' mount. My projector is mounted on the ceiling and the center of the lense is approx. 18" above the center of the screen; it looks spectacular, so there must be some leeway on a horizontal plane as well. In my opinion, naturally centering a lense on a screen will eliminate the need to electronically compensate for trapezoid and maximize the quality of the picture, regardless of the projector. Some projectors may be able to compensate for off-center mounting electronically better than others, but I couldn't tell you which ones.