Anamorphic Lens question - AVS Forum
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post #1 of 7 Old 08-20-2014, 01:38 PM - Thread Starter
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Anamorphic Lens question

Can you keep the projector horizontally offset while using an anamorphic lens? That is either left or right of center within the limits of projector correction?
I'm guessing yes since everyone does it vertically, just want to be sure before I do something silly.
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post #2 of 7 Old 08-20-2014, 04:48 PM
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Originally Posted by netr@cer View Post
Can you keep the projector horizontally offset while using an anamorphic lens? That is either left or right of center within the limits of projector correction?
I'm guessing yes since everyone does it vertically, just want to be sure before I do something silly.
NO (all caps on purpose).

Vertical is fine, horizontal lens shift will seriously affect your image geometry.

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post #3 of 7 Old 08-21-2014, 06:56 AM - Thread Starter
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See, good thing I asked. Thank you for the firm response!

But I am in a pickle now because that is only going to leave me a 12-13' throw and I'm trying to go 130" unless I skip the pool table light
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post #4 of 7 Old 08-21-2014, 04:36 PM
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Originally Posted by netr@cer View Post
See, good thing I asked. Thank you for the firm response!

But I am in a pickle now because that is only going to leave me a 12-13' throw and I'm trying to go 130" unless I skip the pool table light
13' will work but you will have more than a little pincushion. What lens are you using?

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post #5 of 7 Old 08-26-2014, 07:28 AM - Thread Starter
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Originally Posted by John Schuermann View Post
13' will work but you will have more than a little pincushion. What lens are you using?
Nothing purchased yet. In the design phase though I have what I think is close to a final shopping list. Was thinking Sony VPL-HW40ES with a Seymour AT retractable screen with masking. Panamorph doesn't show anything specific for that exact model at this time, so up for suggestions on a good lens at a fair price.

I'm also considering using a 16:9 screen CIW screen instead of CIH, to avoid the anamorphic lens (costs are piling up). A bit of light loss at 2:35, but with the short(er) throw, I should be ok.

Once the rock is up on the wall, I need to tape off the sizes on the wall. In Visio 51" high just doesn't seem like all that much ... .

Some additional challenges:
7' ceiling & main viewing only 10' away from the screen.
I think I'm coming to the realization I might need to downsize the screen a bit....
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post #6 of 7 Old 08-26-2014, 01:58 PM
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Any of the Panamorph lenses except for the FVX200 will work with your setup.

You might want to limit your screen to about 10' wide (130" diagonal, which is what corresponds to your 51" height). That will be very large from a 10' viewing distance for both 16:9 and Scope. That also puts you at about a 3X throw ratio based on the screen height, which means minimal pincushion as well.

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post #7 of 7 Old 09-03-2014, 07:40 PM
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If you are using a cylindrical lens that can be rotated in its mount, the deterioration in screen geometry from horizontal offset is minimized.

Say you are projecting from above/left of screen center. You will need to angle the offset so that the beam points down and to the right.

You will then interpose the anamorphic adapter into the beam so that the center ray of the beam passes through the center of the lens optics.

You will notice a slight dip in the image border in the bottom right corner (the opposite corner to where your projector or placed). The right hand half of the screen will be somewhat wider than the left hand half as well.

By rotating the cylindrical lens the dip in the bottom right corner of the screen can be lessened or gotten rid of altogether, for practical purposes. Often the slight misalignment of verticals that a static grid pattern would reveal after doing this goes completely unnoticed in an actual movie presentation scenario.

You can also slightly change the horizontal offset (so that a 16:9 image is not perfectly centered) and then use the anamorphic lens to re-center the 'scope image. This will lessen the imbalance between the left and right halves of the screen.

Cylindricals are much more adjustable than prism lenses. They can be rotated about the Z axis (center ray of beam), the X axis (tilt up and down) and the Y axis (yaw), and placed slightly out of perfect alignment without apparent image quality penalty, especially in cases of mild misalignment or centering.

This is why many cylincrical lenses have rotational capability (similr to polarizing filters that can be rotated also). You often find that with some adjustment in less-than-ideal conditions the cylindrical lens optics can solve an image problem that, with prism and other unadjustable lenses, only expensive structural work (e.g. knocking out a support wall just to line up the projector) was previously able to do.
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