Originally Posted by AV-NUT-99 View Post
Kind of a general question at this point, but is their any difference in image position/shift range when my RS 640 is shelf mounted (sitting on its four adjustable feet) 5 inches above top of screen as opposed to having it in the same location above the screen, but sitting inverted as it would be with a ceiling mount? I am trying to use lens shift to bring a 2.40:1 image down so that the bottom of the image is even with the bottom of the screen but I do not have enough shift range to accomplish this. I am hoping to use lens memory to have the image at bottom of screen for 2.40:1 images and another memory for a 16x9 image. Consulting the JVC manual did not clarify this for me.
When I did my initial setup with 16x9 image, it seemed that I had to use a lot more lens shift than I expected to get the bottom of the image to line up with bottom of screen. I have done setups with JVC projectors on a coffee table with lens close to bottom of screen and it seems that I am close to the center of the shift range to fit the image to a screen, and same applies when I have used a ceiling mount with the projector inverted and lens center close to the top of the screen.
I cannot lower the shelf position since the projector is in the master BR on the other side of the theaters back wall projecting through a framed opening in the wall. It is mounted as low as possible to clear the top of the BR entry door which is 8 feet tall. Projector is also centered on the screen in it current location. The screen is an SI Solo Pro, mounted to the front wall on wood corbels that allow the screen to extend out enough to clear my 65" Samsung curved TV (I know, curved??? This is a 4K KS9800 which was only available as a curved screen when I bought it) mounted to front wall with a full motion wall mount which closes to about 5 inches away from wall. The Solo Pro clears the retracted TV by about an inch when it is dropped down, with bottom of screen stopping about 2 inches below bottom edge of TV. Screen is 16x9 110" dia, 96"w x 54" high. Projector lens is 17ft 3" to screen surface.
I am assuming that if I invert the projector on the shelf it might fix the problem, but this would not be a suitable option due to the projector being unstable and non adjustable in this configuration. If inverting the projector is a fix, I can use a ceiling mount and nix the shelf mount idea.
Thanks in advance for any insight on this.
Originally Posted by Mike Garrett View Post
You did not give the one measurement needed to confirm everything, but based on what you have given, I can determine inverting on the shelf will work. If the shelf is 5" above top of the screen and not top of the image, then you have exceeded the amount of lens shift available. I am assuming the screen frame is 2" or more? The JVC in your case has 16.2" of vertical lens shift to work with. The measurement that is critical to determine how high above the image the projector can be mounted is the vertical distance from the top of the image to the center of the lens. A measurement from top of the screen frame tells us nothing, unless we know how wide your frame is.
So in your case your projector lens center is frame height + 5" + 4.07" above the top of the image. So you have used 9.07 + frame height of the 16.2" available. For a 2.40 movie the black bars are 7" in height. So when lowering the 2.40 image to the bottom of your screen you are 9.07" + 7" + frame height = 16.07" plus frame height. You only had 16.2" available. So you have exceeded the available amount of lens shift by about the height of your frame. If you inverted the projector on the shelf, you would gain back the shelf thickness plus 4.07". That would be enough to get the 2.40 image to the bottom of the screen.
Originally Posted by bobof View Post
I don't think so. He said he has to shoot the projector through an existing framed hole, so regardless of mounting mechanism the holes stays in the same place. The dimensions of the framed hole, and the position of the shelf in relation to the hole are missing in the discussion.
There may be a difference in the different orientations. Although the specified lens shift is a fixed % either way around the centreline, it could be that there is a bit more shift available at one end than the other due to tolerance in the mech, so mounting it upside down might be helpful.
If he is just talking about turning the projector upside down and placing it on the shelf, that does not help him.
I want to thank everyone for their input. I completed some precise measurements and as currently mounted, my lens center is 2.953 (3) inches above the top of my projected image. While sitting on the shelf, with the feet in place, the lens center is 4 inches above the shelf. If i flipped the projector upside down, with its top sitting on the shelf, the lens center to shelf distance is 2 7/8 inches. So it would seem that I would benefit by flipping it over (either on the shelf or by using a ceiling mount adjusted to be at same vertical position relative to my framed wall opening but with shelf removed). However, by doing so I introduce another issue. By gaining a bit by lowering the lens an inch my projected image would be cut off as I shift the lens down by hitting the bottom of my wall opening frame (lens is sitting about 10 inches back from the front of the framed wall opening since I am trying to leave space for the exhausted air form the projector.)
So it looks like I would be better off just leaving everything as it is. The 16x9 image fits on the screen as is, and the 2.40:1 image sits about an inch above the screen bottom when at full downward shift position. When testing with the projector at the back wall, but within the room and with the lens positioned close to the vertical center of the screen, I really liked having the 2.40:1 image sitting at the very bottom of the screen. It was easy to ignore the unused screen space at the top of the image, and that is what I was trying to accomplish. Since I have an electric drop down screen, I can easily bump the screen up a bit if I find that it bothers me that much. FYI, my finished frame opening is 12" wide by 7" high and 6" deep.