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post #1 of 13 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 13 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 13 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 13 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 13 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 13 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 13 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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post #8 of 13 Old 02-05-2016, 03:48 PM
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Quote:
Originally Posted by John Schuermann View Post
NO (all caps on purpose).

Vertical is fine, horizontal lens shift will seriously affect your image geometry.
I was going to make a thread asking about this, but saw this one so I'll bump it for my question:

I vary my image size using both zooming, and for my widest images I need to use my Panamorph UH480 lens.

My issue is that it's very hard to get the projector centered so perfectly that it zooms out perfectly even to every image size.
So, in other words, I may have a perfectly centered 105" 16:9 image (my masking automatically changes per AR), but once I'm fully zoomed out to say, 116" wide, the image is a couple inches off to one side.

I was therefore thinking of employing a teeny bit of horizontal lens shift (JVC RS600 projector) to center my widest zoom settings. But it seems from John's reply above that I better make sure I have no horizontal lens shift at all when using the A-lens.

If I have this right, this suggests to me that if I'm going to employ any horizontal lens shifting in my other lens memories, I should probably center the image best for use with the A-lens, so no horizontal lens shift is required, and then program lens shift in for other zoomed settings. Does that make sense?

A related question: I'm also having trouble getting the image exactly centered on my A-lens AND getting it zooming out perfectly. Right now the projector seems to have the image hitting the back of the A-lens a bit off center. Is that ok? Is there much leeway as far as where the lens image can go through the A-lens?

Thanks.
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post #9 of 13 Old 02-06-2016, 08:17 AM
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Bumping ^^

Hoping to re-position my projector today so I'm hoping for an answer.
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post #10 of 13 Old 02-06-2016, 02:18 PM
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Quote:
Originally Posted by R Harkness View Post
I was therefore thinking of employing a teeny bit of horizontal lens shift (JVC RS600 projector) to center my widest zoom settings. But it seems from John's reply above that I better make sure I have no horizontal lens shift at all when using the A-lens.
It seems to me, the simplest solution is to square everything up and center it for the largest zoom/image, and then just adjust your masking for everything smaller.

Quote:
A related question: I'm also having trouble getting the image exactly centered on my A-lens AND getting it zooming out perfectly. Right now the projector seems to have the image hitting the back of the A-lens a bit off center. Is that ok? Is there much leeway as far as where the lens image can go through the A-lens?
I think as long as you're not getting any vignetting or other distortion, you're fine. Basically if your lens isn't twisted weird and the light is going though it, you're fine.
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post #11 of 13 Old 02-06-2016, 02:35 PM
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Thanks for the reply!

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Originally Posted by stanger89 View Post
It seems to me, the simplest solution is to square everything up and center it for the largest zoom/image, and then just adjust your masking for everything smaller.
Do you mean adjust my physical (black velvet) masking? If so I can't do that - my side masking doesn't have independent motors to compensate for a slightly shifted image.

If you mean electronic masking - e.g. zoom out my smaller images and mask off the side that overspills, I suppose I might be able to do that, but I may not have enough masking settings to do that and ultimately I'd prefer not to lose any image information.

The problem with centering the image for my largest zoom size is that, as I mentioned, it means the smaller zoom sizes include the size used for 2:35:1 using my anamorphic lens. So if the smaller zoomed size is off, it makes the A-lens image off, and John says using horizontal lens shift to get it centered is a no-no.


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Originally Posted by stanger89 View Post
I think as long as you're not getting any vignetting or other distortion, you're fine. Basically if your lens isn't twisted weird and the light is going though it, you're fine.
Good to know. I didn't know if we really need to hit the sweet spot in the A-lens, right in the middle.
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post #12 of 13 Old 02-06-2016, 07:24 PM
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Quote:
Originally Posted by R Harkness View Post
Do you mean adjust my physical (black velvet) masking? If so I can't do that - my side masking doesn't have independent motors to compensate for a slightly shifted image.

If you mean electronic masking - e.g. zoom out my smaller images and mask off the side that overspills, I suppose I might be able to do that, but I may not have enough masking settings to do that and ultimately I'd prefer not to lose any image information.

The problem with centering the image for my largest zoom size is that, as I mentioned, it means the smaller zoom sizes include the size used for 2:35:1 using my anamorphic lens. So if the smaller zoomed size is off, it makes the A-lens image off, and John says using horizontal lens shift to get it centered is a no-no.
Maybe I'm not understanding the problem them. Ignore the lens for a minute, if you go to the largest zoom setting, and have everything square/normal to the screen, and centered, then all the smaller zooms should be centered as well so long as you don't employ horizontal shift. If that's not what's happening it would say to me that you've got some amount of shift setup there.

Quote:
Good to know. I didn't know if we really need to hit the sweet spot in the A-lens, right in the middle.
It's kind of like lens shift and zoom, yes it's best to be in the middle, the extremes are bad, but in practical terms if you're not introducing any noticeable distortion, you're OK.
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post #13 of 13 Old 02-07-2016, 01:32 PM
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Quote:
Originally Posted by stanger89 View Post
Maybe I'm not understanding the problem them. Ignore the lens for a minute, if you go to the largest zoom setting, and have everything square/normal to the screen, and centered, then all the smaller zooms should be centered as well so long as you don't employ horizontal shift. If that's not what's happening it would say to me that you've got some amount of shift setup there.
Yes the problem is that I can not seem to get perfectly even images with the screen for both zoomed in and zoomed out sizes. This is with the projector having no horizontal lens shift (re-centered to factory center), which is how I've always used this system. So it suggests to me there is some level of off-set in terms of how the projector is centered or facing the screen, but no matter how hard I try I can't seem to find a position that gets it perfect. This is why I was thinking of employing some horizontal lens shift for one end of the zoom range.


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Originally Posted by stanger89 View Post
It's kind of like lens shift and zoom, yes it's best to be in the middle, the extremes are bad, but in practical terms if you're not introducing any noticeable distortion, you're OK.
Righto, I'll just look for distortion. Though I can't avoid some level since I'm at a short throw to begin with.
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