Dual anamorphic lens system - AVS Forum
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post #1 of 23 Old 09-06-2007, 02:47 PM - Thread Starter
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I have a SVGA projector, and have been trying to optically manipulate a 4:3 image (digitally stretched 2.37:1 aspect ratio on a 4:3 fixed panel) for CIH. Although a bit cumbersome, I was able to do it yesterday with the help of two anamorphic lenses--one for vertical compression (panamorph) and one for horizontal expansion (DIY). The results are below. (I will try to replace the screen shots with better images--while I was messing with the lenses, I changed both the color, tint and gamma settings on my Benq, which washed out the picture horribly. Plus, I didn't take the picture with my tripod, so it is a little blurry. In addition, I had some vignetting issues because the aperture on my diy housing was too small, but can be easily corrected) But here it is--proof of concept of cinemascope video for CIH using 4:3 fixed panel projectors:






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post #2 of 23 Old 09-06-2007, 04:37 PM
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Interesting, so:

* the Panamorph does 33% VC from 4:3 to 16:9
* then the DIY lens does a 33% HE from 16:9 to 2.37:1

I don't know how many suitable 4:3 projectors there are for HT anymore, though I can fantasize about giant prisims being used in such a configuration for 4:3 --> 2.37:1 on a CRT PJ

Arrived!:Sam's euro anamorphic AR coated prisimsCurrent experience with: Sanyo Z5, HTPC: ATI 2400Pro|xbox HD-DVD add-on|HD-DVD decryptionPast experience with: Sony 1271, NEC 9PG+, Momitsu V880N
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post #3 of 23 Old 09-07-2007, 11:51 AM
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Quote:
Originally Posted by voicecoils View Post

Interesting, so:

* the Panamorph does 33% VC from 4:3 to 16:9
* then the DIY lens does a 33% HE from 16:9 to 2.37:1

I don't know how many suitable 4:3 projectors there are for HT anymore, though I can fantasize about giant prisims being used in such a configuration for 4:3 --> 2.37:1 on a CRT PJ


well also remember lots of the light cannons for business projectors are 4x3 and are cheaper

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post #4 of 23 Old 09-09-2007, 06:49 AM
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Umm, where did all the other threads go?

EDIT - Never mind, I need to change the display setting in my user profile...

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post #5 of 23 Old 09-09-2007, 07:00 PM
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So much galss though. Any decent contrast ration will go out the window. But then what 4:3 business PJ has HT quality CR. Not to mention the (lack of) source resolution from the panel.
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post #6 of 23 Old 09-10-2007, 08:23 AM
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Quote:
Originally Posted by GetGray View Post

But then what 4:3 business PJ has HT quality CR. Not to mention the (lack of) source resolution from the panel.

Hence his drive for full panel use. I am curious to see what the scaled image looks like before optic manipulation...

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post #7 of 23 Old 09-10-2007, 09:43 AM - Thread Starter
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Sorry, Mark: I promised some more picture, but I haven't been able to get it done yet. Too busy of a weekend, and I spent some of the time getting a new motor in my retractible screen.

I will try tonight if I get a chance...

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post #8 of 23 Old 09-10-2007, 06:30 PM - Thread Starter
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Quote:
Originally Posted by GetGray View Post

So much galss though. Any decent contrast ration will go out the window.

Some people here (CAVX) and others on the DIYAUDIO site were experimenting with dual prisms, in a different way--they were putting two prism pairs together for the two prism elements of a single lens (4 prisms total) and I don't think they were experiencing much loss in brightness. This would be no different, in principle, but the 4 prisms are arranged different, and separated by some air.

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post #9 of 23 Old 09-11-2007, 05:48 AM
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Quote:
Originally Posted by Steve Scherrer View Post

Some people here (CAVX) and others on the DIYAUDIO site were experimenting with dual prisms, in a different way--they were putting two prism pairs together for the two prism elements of a single lens (4 prisms total) and I don't think they were experiencing much loss in brightness. This would be no different, in principle, but the 4 prisms are arranged different, and separated by some air.

The 4 prisms lenses that were experimented with did improve the image at the expense of adding other artefacts to the image such as ghosting. To get the best results requires the prism pairs to be bonded (which I did, and is not cheap if you get a professional glass bonder to do it, which is highly recommended), but to really make a difference requires the prisms to be make from different materials with different refractive indices - and that is where the expense comes in...

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post #10 of 23 Old 09-28-2007, 05:22 AM
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"Tupperware" , the new Duct Tape. haha. I love how we improvise in this hobby. You see guys in here with a $6000.00 projector mounted to whatever household items they can find just to get the thing up before their mount comes in.

How to identify a future projector owner, he's the kid sitting two feet from the 42" plasma.
http://www.avsforum.com/avs-vb/showthread.php?t=954837
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post #11 of 23 Old 09-28-2007, 09:08 AM
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Quote:
Originally Posted by Bruce Wayne View Post

"Tupperware" , the new Duct Tape.

And that is why it is called DIY...

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post #12 of 23 Old 10-18-2007, 11:17 AM
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Technically not on topic, but I have a 4:3 to 2.35:1 HC lens that was made by panamorph. It is one of the original liquid filled models.

I have thought of using it in the game room with an old G10 and my old HTPC for the kids SD viewing.

It looks from you pictures like the combined HC and VE lenses tend to cancel out each other's pincushion and barrel distortion. Is that what it looked like in person too?

Best Regards,
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post #13 of 23 Old 10-18-2007, 06:02 PM
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Quote:
Originally Posted by shodoug View Post

It looks from you pictures like the combined HC and VE lenses tend to cancel out each other's pincushion and barrel distortion.

Good observation I would say that pincushion is still worse than barrel, but it should as you have said cancel (at least in part) some of the edge distortion...

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post #14 of 23 Old 10-18-2007, 06:33 PM - Thread Starter
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Interesting--I had no idea that Panamorph made a 4:3 to 2.35:1 lens. It would make sense, though, and is something that I have been almost able to do with the crystal prisms (can't quite get the angles right--I get to about 2.2:1).

Anyway, I have no idea whether the CA and pincushioning issues were cancelled out with the lens--I didn't have it up long enough to look at that. The pictures are admittedly bad, and I had issues with vignetting because the opening in my DIY lens just wasn't quite big enough to handle.

I will try to set this rig up again and see. Believe it or not, it actually takes quite a block of time to get my pj down and get the prisms all lined up right. I usually don't have a large enough block of time to really sit down and do this--what with 3 kids and plenty of energy whirling around--not something I want to introduce delicate crystal prisms into...

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post #15 of 23 Old 10-18-2007, 06:37 PM
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Apparently, it had three prisms, not the conventional two that the VCs have today...

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post #16 of 23 Old 10-18-2007, 06:58 PM
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Quote:
Originally Posted by Steve Scherrer View Post

I will try to set this rig up again and see. Believe it or not, it actually takes quite a block of time to get my pj down and get the prisms all lined up right. I usually don't have a large enough block of time to really sit down and do this--what with 3 kids and plenty of energy whirling around--not something I want to introduce delicate crystal prisms into...

I really understand what you mean. I have so many projects that I will never get to.

I have yet to try the SMX material that I bought months ago.

Thanks for sharing the pics you had.

CAVX,

The 4:3 to 2.35:1 definitely has some barrel distortion. I was thinking it might work well with the Canon pjs, since IIRC they have some pincushion. Never tried that, either...

Best Regards,
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post #17 of 23 Old 10-18-2007, 08:12 PM
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Keep us updated

You'll love the SmX...

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post #18 of 23 Old 10-19-2007, 11:54 AM - Thread Starter
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Anyone know how the prisms in the three prism 4:3 to 2.35:1 lens were arranged?

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post #19 of 23 Old 10-19-2007, 04:47 PM
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Quote:
Originally Posted by Steve Scherrer View Post

Anyone know how the prisms in the three prism 4:3 to 2.35:1 lens were arranged?

Whilst Panamorph longer manufacture that model, I think the patent is still held by Shawn Kelly, so with respect to him, I don't think it is appropriate to openly discuss that here. There is a link to it in the very first pages of the DIY Audio DIY Anamorphic Lens thread. That lens is also a VC...

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post #20 of 23 Old 11-05-2007, 08:50 PM - Thread Starter
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Ahh--I finally had a few minutes to tweak my dual set up and really see if this thing would work. With my ceiling mounted projector and Panamorph, I held the horizontal expansion lens up in front of the panamorph to get the dual stretch (er, vertical compression/horizontal stretch). Here are some of the results. I took the pictures with a little bit of light on so you could see the screen, and see the difference between the single lens non-stretch version and the dual lens. I have included one in stretch-o-vision so you could see how the stretch appears prior to me holding the second lens in place.

First: Single anamorphic lens (only Panamorph):


Second: Stretch-o-vision: Benq full panel stretch with single anamorphic lens (remember, my benq is 4x3 projector):


Third: Dual anamorphic lens (one thing I have noticed, my Benq actually cut off the bottom a little on the stretch--not sure if I am using the right setting, but it's close enough to demonstrate that this actually works!):

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post #21 of 23 Old 11-06-2007, 12:01 AM
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Quote:
Originally Posted by Steve Scherrer View Post

one thing I have noticed, my Benq actually cut off the bottom a little on the stretch--not sure if I am using the right setting, but it's close enough to demonstrate that this actually works!

Interesting result Steve. The slight cutoff is mostlikely due to 33% Vertical Stretch Vs 25% Black Bars - something has to give...

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post #22 of 23 Old 11-06-2007, 07:15 AM - Thread Starter
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One thing I will probably do is make a simple case where the prisms are permanently in place, as opposed to the adjustable one that I have now. The adjustable one makes me a little nervous that the prisms will just fall out if the clue fails on the posts that are adhered to the top and bottom of the prisms. I can just make a rail that moves it in and out of position.

I did notice a lessening of brightness and a slight color shift with the second lens in place. Next step is to get this up so I can refocus and recalibrate.

I also have to fix the curl on the edges of my screen. It hasn't been an issue before with the image sitting in the middle of the screen and not going edge to edge, but if I am going edge to edge with CIH, then I have to add tensioners or something. Lot's to work on! But this is great--a lot of fun!

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post #23 of 23 Old 11-12-2007, 09:15 AM - Thread Starter
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Just an update--I spent some time putting the prisms into a case and getting it up in front of the projector--Completely thrilled at the results so far.

I had used rotatable prisms to start because I was hoping to get stretch from 4:3 to 21:9, but it turns out it made everything needlessly complicated. When I paired the two lenses together (Panamorph and DIY), I decided to go with the permanently mounted prisms, but not having the ability to adjust the angles was a bit of a bear. I had to keep putting the prisms in the case, screwing everything down tight, then when the angles weren't right, had to remove the case to adjust the prisms! I must have done this about 6 times to get the prisms dialed in correctly.

Anyway, next step is to get some kind of mounting system for the case on my ceiling for the projector.

Will supply some photos soon.

(Of course, this can be done without the Panamorph, with four prisms in one case...)

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