The Tokina Canon EF to PL Mount 1.6X Expander will not work because it is meant to adapt EF-S lenses to full frame cameras. The C300 and the C700 are both Super 35 cameras. thus this will not work.

It is not. This adapts Canon EF Lens to a PL-Mount Camera. The Pocket Cinema Camera 6K is an EF mount camera.

This adapter is meant for Super35 EF mount cine lenses so they can be used on a full frame sensor camera with a PL mount. This comes with caveats. As a consequence of the image being blown up in size to cover the full frame sensor, the FOV (Field of View) narrows for it has been magnified. This may require you to get a wider-angle lens. Then you lose 1.36 stops of light using this. Lastly, the lens needs to have at least a T/2 exit pupil aperture so the light can spread enough. Paradoxically, this T/2 sized exit pupil is still needed when you set the lens to the required T/2.8 or higher number that is needed for this adapter to deliver quality. There is no information as to using Canon full frame EF lenses. I would say that such a lens will mount, that the image will still be blown up and you will still lose wideness. However, I know of no Canon EOS EF lenses that have manual aperture to fulfill the requirement of a T/2 exit pupil and then being able to stop down to T/2.8 or more.

The Tokina Canon EF to PL Mount 1.6X Expander is designed to work with Canon EF mount lenses. The EF-S mount has a flange that will dip too low into the adapter and will not allow it to mount to it.

Not that we are aware of. This is designed for cameras that have a full frame sensor which is 6-8K in resolution, such as select RED cameras.

The Tokina Canon EF to PL Mount 1.6X Expander uses the principle of an tele-extender to expand the image circle of a Super35 lens so that it covers the larger full frame image circle. But what it is really is a method for mounting a EF lens on to a PL mount camera.

Yes, the Tokina Canon EF to PL Mount 1.6X Expander can be used on full-frame cameras like the ARRI ALEXA Mini LF and Lens Mount Set (LPL).

No, The Design of this adapter works best with S35 lenses. The Tokina 1.6x Expander magnifies the image circle of S35 lenses, expanding them to cover larger FF35 or Vista Vision sensors. The Tokina 1.6x expander has the best performance when used with lenses that have a T2.0 or larger aperture and when the lens is stopped down to T2.8 or smaller.