Originally Posted by BobL
Using the digtal keystone control does not alter the distortion, it only crops the picture to make a rectangle.
With all due respect, I'm going to have to disagree with this statement.
Turn on your projector, get a picture with some large text displayed and paused (text only because it is easier, but feel free to use someone's head or a building if you'd like) ... measure the width of that object.
Now, start keystoning.
Take some measurements along the way.
This object, be it a head - word - letter - building - whatever, is going to adjust in size depending on how much keystoning you perform. That, by it's very nature is altering and distorting the image.
On a side note, gwlaw99, a few years back I wrote an article about keystone correction. I had some nice examples of the image distortions. I even had some nice digital pictures of face close-ups that showed pupils of eyes completely disappear with keystoning.
I'll see if I can dig them up when I get to the office on Monday.
DISCLAIMER - I am not by any means stating that keystone is going to completely mess up a projected movie. I am just stating that it does, in fact, effect picture quality. I realize that some folks would never notice or be bothered by it.