Horizontal Lens Shift Usage, Effects

StephenM · Mar 13, 2021

I was wondering if anyone had any experience with using horizontal lens shift in projectors to correct offsets due to locations of projectors. I am currently having an issue designing a home theatre with the projector dead center. The issue is due to impact noise from walking above effecting the projector mount. My ceiling is below the kitchen so its a well used room.

I have an alternate option where I would build a ceiling box/shelf. But it would help to shift this box closer to the side wall. From reading up on using horizontal lens shift, all suggestions say don't use it. Is there a usage case where it may work without issue? Right now I am focused on using the JVC NX5, but i would have to switch to the Epson 6050 because it has much bigger horizontal lens shift. I would have liked to use the JVC but there is just not enough lens shift and it is a bigger to ceiling box.

BMXTRIX · Mar 15, 2021

Horizontal lens shift is no different than vertical lens shift. If you have a projector with lens shift, you are ALWAYS using it. That is, you are shifted to the top, bottom, left, right, or center, or somewhere in between. It isn't a digital correction, but an analog one.
So, with a well designed lens system, you should always be able to use lens shift, all the way to the extents of the lens shift available, and you should not have any focus or image uniformity issues.
That said, not all lenses actually deliver. Epson is known for being good, but not perfect. Sometimes lens shift does introduce some issues. So, it is recommended to always avoid the extents of lens shift whenever possible.

BE AWARE: You can't use the maximum horizontal and vertical lens shift at the same time. Lens shift operates in a circular pattern. Why? Because lenses are round. So, if you have the projector tight to the ceiling, you can't also slide it a full screen width to the left or right.

Not sure if this link is working, but the Jack Liu calculator is one of the best I've ever seen when it comes to including lens shift capability...