Your best option depends on how you intend to post produce your content. If you have a real powerful post production system, us the Canon product. On the other hand if you have a not to cool system, cropping the 16:9 image to 2.35:1 aspect ratio will probably be the easiest way to work.
The product name for the Canon product is the ACV-235 Anamorphic Converter, has a list price of $29,500 dollars and there is no evidence that its use degrades the image optically in any way. This item is for 2/3 image size format 16:9 HD lenses and cameras and squeezes a 2.35:1 aspect ratio image into a 16:9 aspect ratio image. Similar to the Angenieux converter "CLA 35 HD", it causes the resulting image to be upside down. A powerful postproduction system will be able to unsqueeze the image back to 2.35:1 and turn the image right side up without a problem.
Please be advised that real cinematographic anamorphic images are 2.40:1 aspect ratio (when shot using Panavision Anamorphic lenses.)
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