Vertical Lens Shift

[mitchok]

Does anyone have a good general reference/discussion for vertical lens shift (VLS)? I know that each projector is different in the amount of VLS it is capable of. The basic issue is that I have a complicated ceiling/roof line issues for the future home of the MitchOK Theater. I am beginning to draw it out and do some geometry to determine approximate placement. I was confused by the EPSON Powerlite Pro Cinema 1080 (a possible candidate) specifications...

On the Epson site it says...
Lens Shift Range
Vertical ±96%

Yet, when you read the users manual, it shows for example (16:9 aspect ratio),
Projection Distance: 11.8 to 25.1 feet
max diag: 120 in (106w x 59h)
Vertical Offset: 27.2 to -27.2 inches (from lens centerline)

To me, ±27.2 inches from lens centerline doesn't equate to ±96%. If you take (27.2 inches) divided by 59 inches that only equals 46%. Obviously, I am not figuring this right or understanding it right.

In addition, I don't really want to max out the vertical shift and I am planning a ceiling mount that will provide some vertical adjustment. Any help on the subject would be great.

MitchOK

[bpape]

They're off a little - but that's actually 92% (you have to double the 27.2) and that's at max diagonal so anything smaller would be higher.

Bryan

[mitchok]

Right... but that is 92% full scale or ±46%... not ±92%. I think I am goiing to work to exact dimensions in the users' manuals. Thanks Bryan.

[bpape]

Oops. Yup, you're right. Sorry 'bout that.

Bryan