[greg1292]

I want to to buy this lens and use it with the projector. The size screen would be 10 ft wide.

throw 159 inches. I know I am on the boarder since they recommend 14 feet back I will miss it by less than a foot. Will the geometry be close enough that the pincusion won't be extreme with this lens?.


Thanks

 

[Nasty N8]

Should be fine at that length just some off into the border you will never know it was there.


Nate

 

[greg1292]

Thanks for the info. I went ahead and ordered one.

 

[greg1292]

I received my lens today and am going to set up. Is it better to ceiling mount or shelf mount?


I currently have it shelf mounted and have some extreme pincushion but when I shift the image down to the bottom part of the screen it all but goes away! Is there some sort of offset that is needed or do I need to mount the projector up higher. I think I might have answered my own question but am trying to understand the why aspect.


Throw is 165 inches screen 11ft.

 

[usualsuspects]

Projector height should not matter as long as there is no keystone without the lens in place. When the lens is in place, it needs to be parallel to the beam path (pointed downwards for a ceiling mount or less downwards for a slightly higher than vertically centered shelf mount). Whatever lens mounting position induces the least amount of distortion is the correct one

, but moving from a shelf mount to a ceiling mount should not be a factor in image quality/distortion.

 

[greg1292]

So the lens must be centered to the screen and image pefectly square and symetrical. Do I measure this with a tape measure?

 

[usualsuspects]

1) align projector. Up/down lens shift is ok and makes no difference. Left/right is critical - you want the projector lens exactly in the horizontal center of the screen w/o any left/right lens shift.


2) align lens. You want the image centered top/bottom/left/right on both the entrance (back) side and the exit (front side). Take a look at how the lens is tilted. Example - If the projector was mounted w/o vertical lens shift or projector offset (vertical center of screen), then the faces of the lens should be straight up and down - no tilt. The more the projector is mounted off center vertically, the more the lens needs to be tilted.


A tape measure is helpful in getting the projector mounted by measuring the distances from the lens to the left/right sides of the screen, they should be exactly the same. A tape measure is useful for measuring the image distortion after the lens is in place. You would measure the actual projected image on the screen to see how symmetrical the distortion is.


There are three planes of possible lens adjustment - roll / pitch / yaw.

Roll should be zero. Pitch depends on how far off vertical center the projector lens is. Yaw should be zero. You want the UH380 as close as possible to the projector lens - 1/8" is about as close as is reasonable - the farther away the UH380 is from the projector, the more distortion you will have.


It can be frustrating and take quite some time to get it adjusted if you have never done it before, just hang in there and you will get it. You will likely find that it is counterintuitive about what way to move the lens to get the desired effect at first.

 

[ca1ore]



Quote:
Originally Posted by greg1292 /forum/post/12982781


I currently have it shelf mounted and have some extreme pincushion but when I shift the image down to the bottom part of the screen it all but goes away!

You will have to play around a bit with the angle of the lens. I found with my U380 that the barelling on the sides (I assume this is what you mean by pin-cushionning) is significantly reduced when the projector light beam passes through the lens at an angle.


My projector is ceiling mounted, pointing level at the screen, the lens is about 1/4 inch from the projector which allows me to angle it down a bit (the lens 'points' at the bottom edge of the screen) which minimizes the barel effect.