French prism article - AVS Forum
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post #1 of 8 Old 04-03-2012, 05:58 AM - Thread Starter
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Hello all!

Few years back I made an article about the "DIY anamorphic lens". It was all in Finnish so it would not have any use for you. Now I founded again my first drafts so I decided to translate it to english and put it here. I cannot post the the final version of the document, but the basic idea is the same.

It made the translation pretty quickly so there will be spelling mistakes but the major idea is quite clear.

The document is about 2,5MB so I had to make to remove few pictures and spilt the document.

Again sorry about the long time. Even the topic for the french prisms was closed

Hopefully somebody will read it. Please feel free to comment.

Thanks
Mika Myrberg

 

DIY anamorpic lens part 1.doc 158k . file

 

DIY anamorpic lens part 2.doc 416.5k . file
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post #2 of 8 Old 04-03-2012, 02:21 PM
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thanks for this I am going to be building mine this week!!!

Are you still using yours?
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post #3 of 8 Old 04-03-2012, 11:05 PM - Thread Starter
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I would if my new house would allow it. There is just not enough space where I could use it. But before I moved I used it 100% of the time (except when I watched TDK).
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post #4 of 8 Old 04-04-2012, 04:07 AM
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I think TDK is quite acceptable in Scope because all of the IMAX scenes were framed to match with the rest of the Scope film.

These prisms are small, but do have an optic surface finish and optic coating so should (whilst not perfect) give better results than the "trophies" used in many DIY anamorphic adapters.

CA will always be a problem because of the fact that these prisms are made from just one type of glass.

Astigmatism correction requires either special additional lenses or curved surfaces ground into the prism. If one was to take the time and effort to do that, one might just consider cylindrical lenses a better alternative.

Grid Distortion will always be worse with this type of design.

Mark Techer

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post #5 of 8 Old 04-08-2012, 06:58 PM
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Quote:
Originally Posted by CAVX View Post

These prisms are small, but do have an optic surface finish and optic coating so should (whilst not perfect) give better results than the "trophies" used in many DIY anamorphic adapters.

What's the concern with having small sized prisms? Will we lose some light?

Quote:
Originally Posted by CAVX View Post

CA will always be a problem because of the fact that these prisms are made from just one type of glass.

Can CA be reduced if one of the prisms were made of another material, or would we need to form two achromatic doublets?
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post #6 of 8 Old 04-08-2012, 08:39 PM
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Quote:
Originally Posted by b_123 View Post

What's the concern with having small sized prisms? Will we lose some light?

Vignetting is the main concern.



Quote:
Can CA be reduced if one of the prisms were made of another material, or would we need to form two achromatic doublets?

Achromatic Doublets are the minimum needed for CA correction.

Mark Techer

I love my Constant Image Height system!
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post #7 of 8 Old 05-04-2012, 08:23 AM
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Quote:
Originally Posted by CAVX View Post

These prisms are small, but do have an optic surface finish and optic coating so should (whilst not perfect) give better results than the "trophies" used in many DIY anamorphic adapters.


Shoot! - I'm afraid I may have ordered the wrong crystal wedges for my DIY lens. Specifically, I ordered the "J24" - 4"x6" crystal wedges from Massilon Plaque - cost about a $100 shipped. Should I have ordered the ones from SurpluShed instead? I placed an order for the Massilon crystal wedges yesterday so I may still have time to cancel.

Any thoughts anyone?

Thanks,
Dhar
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post #8 of 8 Old 05-05-2012, 04:20 AM
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Quote:
Originally Posted by Efalegalo View Post

Shoot! - I'm afraid I may have ordered the wrong crystal wedges for my DIY lens. Specifically, I ordered the "J24" - 4"x6" crystal wedges from Massilon Plaque - cost about a $100 shipped. Should I have ordered the ones from SurpluShed instead? I placed an order for the Massilon crystal wedges yesterday so I may still have time to cancel.

Any thoughts anyone?

Thanks,
Dhar

As I mentioned, you should get better results from the SS (French) prisms because they have both a proper optical finish as well as optic coatings.

Mark Techer

I love my Constant Image Height system!
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