Gaumont-Kalee Varamorph lens - AVS Forum
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post #1 of 10 Old 06-12-2014, 09:57 PM - Thread Starter
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Gaumont-Kalee Varamorph lens

I bought one of these for $95 of ebay and I just have to share it.
The internal prism lenses were in pristine condition, I took it apart and to my surprise it is a 5 prism setup on lens (one prism to adjust for CA), I reconfigured the lens into a smaller case as the original case was to large and heavy. Once in place the image quality of this lens has blown me away. As soon as I make the screen and position lens better. I will upload some screen shots.

So if you want a excellent DIY Anamorphic lens then look for it on Google. you might get lucky

Also, I used a triumph TR7 pop up headlight mechanism so I could remotely move the lens in and out of the image path. This will soon be operated via a USB relay on the HTPC

Regards
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post #2 of 10 Old 06-13-2014, 03:33 AM
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Quote:
Originally Posted by neoridium View Post
The internal prism lenses were in pristine condition, I took it apart and to my surprise it is a 5 prism setup on lens (one prism to adjust for CA)
Good find. You will find that each prism is a CA corrected "doublette" to correct CA. This means that each prism is made from two types of glass and if you look at your image you can see the bond line.

So as it stands, this is a 4 element adapter.

Is there an Astigmatism lens for this? If it had that, it would be a 5 element unit.

Mark Techer

I love my Constant Image Height system!
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post #3 of 10 Old 06-13-2014, 04:16 AM - Thread Starter
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Quote:
Originally Posted by CAVX View Post
Good find. You will find that each prism is a CA corrected "doublette" to correct CA. This means that each prism is made from two types of glass and if you look at your image you can see the bond line.

So as it stands, this is a 4 element adapter.

Is there an Astigmatism lens for this? If it had that, it would be a 5 element unit.
One of the prisms has one bond line and the other one has 2 bond lines... so I thought that the 5th element corrected for CA, hmm... so it corrects Astigmatism. Thanks CAVX I did not know that. I'll see if I can find a better photo of both prisms
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post #4 of 10 Old 06-13-2014, 07:39 PM - Thread Starter
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Hi Mark,

I found this drawing of the lens arrangement, and I added another photo where you can see the two bond lines. So the 5 the element is for Astigmatism. So is this why I am getting such a good image from this lens?

Carey
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post #5 of 10 Old 06-13-2014, 08:33 PM
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Quote:
Originally Posted by neoridium View Post
One of the prisms has one bond line and the other one has 2 bond lines... so I thought that the 5th element corrected for CA, hmm... so it corrects Astigmatism. Thanks CAVX I did not know that. I'll see if I can find a better photo of both prisms
So one is a doublet and the other is a tripplet? Astigmatism correction is a prism based system requires at least one of the prism faces to be curved which these do not appear to be.

Project a grid and take a screen cap.

Mark Techer

I love my Constant Image Height system!
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post #6 of 10 Old 06-13-2014, 10:16 PM - Thread Starter
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Hi Mark,

I have attached two below, one image I used from your blog to test (I hope you don't mind). The lens isn't fully adjusted and also the photo is from my phone so the picture isn't that good.

Carey
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post #7 of 10 Old 06-17-2014, 03:50 AM - Thread Starter
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Quote:
Originally Posted by CAVX View Post
So one is a doublet and the other is a tripplet? Astigmatism correction is a prism based system requires at least one of the prism faces to be curved which these do not appear to be.

Project a grid and take a screen cap.
Hi Mark,

I made a grid pattern using RGB and white, each coloured line is only 1 pixel wide, this is picture 2 (I took it on the far right side of the image to show it at the worst position). Picture 1 is a photo of Oblivion. Oh and the image is projected on a white concrete wall at the moment with a crudely painted black border (just for testing).

I looked everywhere and can't find what the 3rd prism (5th element) is for. I have emailed the widescreen museum (http://www.widescreenmuseum.com/widescreen/wingvv2.htm) as it is the only place I have found information on this lens. Hopefully they might know

Carey
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post #8 of 10 Old 06-20-2014, 04:49 AM
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Well I hope they reply. For prisms, it seems to be producing a very clean image.

Mark Techer

I love my Constant Image Height system!
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post #9 of 10 Old 06-23-2014, 07:57 PM - Thread Starter
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Originally Posted by CAVX View Post
Well I hope they reply. For prisms, it seems to be producing a very clean image.
Hi Mark,

After a few emails, I found out from the widescreen museum site that the lens was made by Taylor, Taylor & Hobson. I also found out they still operate but no longer make lenses for the movie industry, however, Taylor Hobson did direct me to Cooke Optics. Cooke Optics was formed by stakeholders of Taylor Hobson, they bought out that part the business and still operate today making cinematography lenses.

The reply I just received from Cooke Optics was the following…

“You have a beautiful piece of optics. These variable cinema projection anamorphic lenses were originally designed and built by Rank Taylor Hobson in Leicester to support the prestigious Visatvision project that the Rank cinema chain developed with Columbia pictures in the US (that subsequently got overtaken by Cinemascope).

The projectors that carried these lenses were made by the Rank Kershaw company in Leeds in the UK (Kalee = Kershaw Abe LEEds).

You obviously realise that the lens you have achieves its anamorphic effect by using prisms, and yes, there is a doublet prism and a triplet prism, with a (spherical) collimating lens at the projector end of the assembly and a (spherical) focussing lens for different screen distances at the screen end of the assembly.

The three and two component prisms are principally to correct higher order chromatic aberration (secondary spectrum and transverse chromatic aberration), but of course the whole assembly has to be designed to balance all the usual aberrations, including astigmatism. These anamorphic projection lenses just don't work unless the prismatic anamorphic section is working in collimated (aka parallel) light, this why the prisms don't introduce any astigmatism and the front (spherical) optic is left to focus at different screen distances.


Carey
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post #10 of 10 Old 09-05-2014, 03:31 PM
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Could this conceivably be done with other variable anamorphic lenses such as Hi-Lux, or Tushinsky? And if so, would it be worthwhile?
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