If 100" x 56.25" = 16x9 Then Why...

I decided to make my screen 100" wide.

Therefore I multiplied 100 x 9 / 16 and got 56.25 for the height.

I then made the borders wider on my 120" retractable screen so that the image area is 100" x 56.25" exactly.

The problem is I can't seem to get images that I think are 16:9 to fit the screen area. I should mention that I have to do some keystone correction to square up the image since I do not have lens shift. I usually use the main menu of the Terminator II DVD to fit the image to the screen.

Questions:

Did I do the math right?

Does the keystone correction screw up the aspect ratio of the image?

On most DVDs, are the main menus 16:9 or are they that funny size that has narrow bars top and bottom.

Is it possible that there is something odd about the HD72?
It is actually 1280x768 resolution.

I would think the best course of action would be to make the screen 16:9 and live with the miss fit since I am likely to replace this projector with a 1080p unit when the bulb burns out. Sound reasonable?

Thanks in advance for any suggestions as to what may be wrong.

I could make the borders match this particular projector but repainting for each projector is not really an option. My preference would be to make a proper 16:9 image area and if this projector does not fit it properly when running in 16:9 mode then I will live with it.

I am well ware that the projector is native WXGA and I run it in 16:9 mode. For 720p content the image occupies 720 pixel in height and the projector allow you to shift it up and down within the 768 pixels. Thinking about this has made me realize that I should find something with true 1280x720 content and then shift the image to the max vertically. I may find that I do not need to tilt the projector as much.

The problem is that in 16:9 mode the image seems to be a bit too wide for the height of the screen. I have noticed as Laserfan pointed out, that some content is 1.85:1 which is close to 16:9 but a bit smaller in height. This leads to small bars top and bottom on a 16:9 screen.

I think what I need to do is find a DVD that I am sure is 16:9 and then fit the image properly to the screen. By using maximum digital vertical image shift I may be able to minimize the projector tilt and therefore reduce the keystone correction.

Kbgl mentioned tilting the screen. I have often wondered why people don't consider this option when they don't have vertical lens shift. This would be particularly easy when you make a floating screen that sits in front of a black wall or drapes.

Simply tilt the screen downwards until the image is squared on the screen. I suspect in most cases the screen would actually end up being perpendicular to the viewer's line of site.

As you can see from this photo I had considered tilting my screen in the beginning.



One advantage to a retractable screen is that you can retract the screen to fit the lower edge of the image. I know that means that the border only fits the sides and bottom but better that then the bars top and bottom.

I think you could get away with adjusting the height of the image area by applying tap across the bottom of a retractable screen. Applying it to the edges would cause problems as the screen is rolled up. The difference in thickness across the screen roll would lead to worse waves etc.

That's a good question! I don't know.