DIY anamorphic lens - Page 4

chainsaw · 8th August 2002, 11:20 AM

so the larger water prism is the one that is placed infront of the projector lens ?

I just noticed that my vt540 has the air vents blowing out the hot air directly under the lens ! I wonder if this will be a problem !

tahustvedt · 8th August 2002, 01:17 PM

No, the smallest turpentine-prism should be closest to the projector-lens. The projection-beam wouldn't fit inside the prisms if the small prism is farthest from the projector.

I don't think the heat would be a problem as long as it doesn't blow directly at the prisms.

Tor Arne

rwhitley · 9th August 2002, 12:26 AM

Mineral Oil has the same (or very close) refractive index, so in terms of the compression of the picture it should work. The question is more on dispersion.

The water prism causes a blue blur, the turpentine a red one so they offset each other. The mineral oil may not do this as well, however the Panamorph uses minerial oil so it likely does as good or better a job.

I am currently having focus problems with prototype 1.5, but I believe my 24 degree angle prism may be more like 26.5 degrees (can't seem to find my protractor and I keep forgetting to buy a new one). If this is the case, would this potentially cause my focus problems?

Rick

tahustvedt · 9th August 2002, 01:52 PM

I don't now. I don't get any problems with focus with my non-corrective lens, but my corrective lenses have so far been impossible to focus completely. The less correction the better the focus has been though.

I still haven't made any new parts, I'm flying south to visit myparents today so I won't be able to do any work this weekend either.

Tor Arne

woneill · 11th August 2002, 11:18 PM

Tor,

I am crap at glueing things - especially where liquids are concerned, so I went and bought a cinema anamorphic projection lens cheap off Ebay.

I'm crap? Yeah, but I found out something interesting:

Your issue about focus shift between top and bottom is something the designers of this lens faced, and they solved it by having TWO sets of corrected prisms.

Yup, there are two identical prism combinations in my apparatus (each a prism doublet corrected for chromatic aberations) - the first set shifts upwards, and the second set, arranged upside-down, shifts downwards again.

The trick is to angle the two sets so that the shifting and compression is even in both directions (up and down) and thus the image is largely undistorted. Each prism only provides half of the anamorphic compression, resulting in a really nice image.

Hope this helps.

Keep up the good work,

Bill.

tahustvedt · 12th August 2002, 02:37 PM

Cool!

What lens was that? The Super Panatar?

Tor Arne

woneill · 12th August 2002, 04:46 PM

Hi Tor,

I don't exactly know the details. It was sold as a "Hilux" and adjusted for a 200ft throw, but other than that I don't know more than I can tell from simple observations.

It doesn't have any lenses as such - just the two sets of prisms. It is about a foot long and four inches in diameter (obviously not intended for a very wide-angle setup), and on first tests produces a very nice image on my wall despite the fact that it needs a real good cleaning. (I'm also going to put a tripod mount on it so that it is fully compatible with my OHP-style optics.)

I manually tweaked the angles on the prism sets until they were balanced and gave the appropriate compression, and sat down to enjoy The Matrix...

I was also thinking of your corrective problem, and am wondering whether it would be better to use a converging lens on input to your system, and a diverging lens on exit. (I might try this on mine if I spot any annoying effects once the rose-coloured spectacles come off.)

The idea is that if you can counteract the divergence of the beam on entry to the system, and then re-apply that divergence on exit, you would be working with parallel rays through the prisms.

You would need to match the converging/diverging lenses with each other and with the focal length of your projector, but it might be a good alternative to trying to glue bent tensioned pieces of glass...

Bill.

Michael F T · 12th August 2002, 08:36 PM

Is the lens like this??
Sounds the same.
Where did you get a double prism lens?

http://www.widescreenmuseum.com/widescreen/wingtr2.htm

woneill · 12th August 2002, 09:27 PM

no, more like this:

woneill · 12th August 2002, 09:29 PM

And this:

8th August 2002, 01:17 PM	#32
tahustvedt diyAudio Member Join Date: Jul 2002 Location: Norway	No, the smallest turpentine-prism should be closest to the projector-lens. The projection-beam wouldn't fit inside the prisms if the small prism is farthest from the projector. I don't think the heat would be a problem as long as it doesn't blow directly at the prisms. Tor Arne __________________ Website: http://home.c2i.net/ahustvedt

9th August 2002, 01:52 PM	#34
tahustvedt diyAudio Member Join Date: Jul 2002 Location: Norway	I don't now. I don't get any problems with focus with my non-corrective lens, but my corrective lenses have so far been impossible to focus completely. The less correction the better the focus has been though. I still haven't made any new parts, I'm flying south to visit myparents today so I won't be able to do any work this weekend either. Tor Arne __________________ Website: http://home.c2i.net/ahustvedt

12th August 2002, 02:37 PM	#36
tahustvedt diyAudio Member Join Date: Jul 2002 Location: Norway	Cool! What lens was that? The Super Panatar? Tor Arne __________________ Website: http://home.c2i.net/ahustvedt

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8th August 2002, 11:20 AM	#31
chainsaw diyAudio Member Join Date: Aug 2002 Location: Sydney	so the larger water prism is the one that is placed infront of the projector lens ? I just noticed that my vt540 has the air vents blowing out the hot air directly under the lens ! I wonder if this will be a problem !

9th August 2002, 12:26 AM	#33
rwhitley diyAudio Member Join Date: Jul 2002 Location: Ottawa	Mineral Oil has the same (or very close) refractive index, so in terms of the compression of the picture it should work. The question is more on dispersion. The water prism causes a blue blur, the turpentine a red one so they offset each other. The mineral oil may not do this as well, however the Panamorph uses minerial oil so it likely does as good or better a job. I am currently having focus problems with prototype 1.5, but I believe my 24 degree angle prism may be more like 26.5 degrees (can't seem to find my protractor and I keep forgetting to buy a new one). If this is the case, would this potentially cause my focus problems? Rick

11th August 2002, 11:18 PM	#35
woneill diyAudio Member Join Date: Jun 2002 Location: Somewhere in Sunny NJ	Tor, I am crap at glueing things - especially where liquids are concerned, so I went and bought a cinema anamorphic projection lens cheap off Ebay. I'm crap? Yeah, but I found out something interesting: Your issue about focus shift between top and bottom is something the designers of this lens faced, and they solved it by having TWO sets of corrected prisms. Yup, there are two identical prism combinations in my apparatus (each a prism doublet corrected for chromatic aberations) - the first set shifts upwards, and the second set, arranged upside-down, shifts downwards again. The trick is to angle the two sets so that the shifting and compression is even in both directions (up and down) and thus the image is largely undistorted. Each prism only provides half of the anamorphic compression, resulting in a really nice image. Hope this helps. Keep up the good work, Bill.

12th August 2002, 04:46 PM	#37
woneill diyAudio Member Join Date: Jun 2002 Location: Somewhere in Sunny NJ	Hi Tor, I don't exactly know the details. It was sold as a "Hilux" and adjusted for a 200ft throw, but other than that I don't know more than I can tell from simple observations. It doesn't have any lenses as such - just the two sets of prisms. It is about a foot long and four inches in diameter (obviously not intended for a very wide-angle setup), and on first tests produces a very nice image on my wall despite the fact that it needs a real good cleaning. (I'm also going to put a tripod mount on it so that it is fully compatible with my OHP-style optics.) I manually tweaked the angles on the prism sets until they were balanced and gave the appropriate compression, and sat down to enjoy The Matrix... I was also thinking of your corrective problem, and am wondering whether it would be better to use a converging lens on input to your system, and a diverging lens on exit. (I might try this on mine if I spot any annoying effects once the rose-coloured spectacles come off.) The idea is that if you can counteract the divergence of the beam on entry to the system, and then re-apply that divergence on exit, you would be working with parallel rays through the prisms. You would need to match the converging/diverging lenses with each other and with the focal length of your projector, but it might be a good alternative to trying to glue bent tensioned pieces of glass... Bill.

12th August 2002, 08:36 PM	#38
Michael F T diyAudio Member Join Date: Aug 2002 Location: NY NY	Is the lens like this?? Sounds the same. Where did you get a double prism lens? http://www.widescreenmuseum.com/widescreen/wingtr2.htm

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