How many non-canon lenses have you purchased for your 5D Mk II video needs?

[Gary Szunyogh]

Mylar, as in balloon material?

Originally Posted by Mark Hahn

a dissenting opinion...

I'm buying zero nikon lenses because I want to use my expensive L lenses for video. I have been twisting the lens, which works well, but I have an idea for a thin Mylar insulator to isolate the lens electronics. I'm going to cut it into a disk with the inner and outer diameters just right for fitting in the mount without getting in the light path. Then the lens cannot fall off, and there is no chance of junk from adhesive tape getting into the camera.

I will lock the lens onto an aperture while removing the lens, place the Mylar disk in the mount, and remount the lens. I will post my results. Now I just have to find out where to get Mylar plastic.

[Mark Hahn]

Originally Posted by Gary Szunyogh

Mylar, as in balloon material?

Mylar is a polystyrene plastic that is very strong and stretch resistant. Even in 0.00048 inch thick sheets it can handle a lot of force without deforming. For balloons, they sputter a layer of aluminum on the inside surface to make it reflective but mainly to hold helium in. The aluminum is also so thin the material stays somewhat flexible.

Mylar's second biggest use is as an electric insulator. Mylar capacitors are electronic devices that have very thin Mylar of great length rolled up with an electrolyte in the layers. Even though the Mylar is thin, it can block up to thousands of volts. It is also strong so none of the electrolyte can leak through and short out the capacitor.

These insulating and strength properties make it perfect for what I'm going to try to do. It will provide a layer of insulation between the pins on the camera and the lens contacts. It can do this even when very thin.

The thinness is of utmost importance since thickness in the disc might cause the mount to be too tight and might even freeze it in place after turning the lens too hard. Luckily Mylar is also a slippery plastic so the lens should be able to rotate smoothly while mounting or demounting. It is also used to line pipes to reduce friction, like Teflon. (Can you tell I like Mylar?)

The strength is important so the Mylar isn't shredded by the mount as the lens is screwed in. I will experiment with different thicknesses, starting at 48 gauge (0.00048 inches). With luck this thickness will be strong enough and I'm quite sure that is thin enough to allow the lens to close when mounting.

I did some googling for Mylar but I haven't found a supplier for a small qty yet. Office supply stores and art/craft stores carry it, but I fear they will only have 300 to 500 gauge film which is used for overlays, stencils, printing on ink jets or lasers, etc. I want to start my tests with 48 gauge, then 100, then 150, etc.

I will probably start with the smallest I can find in local stores and be careful not to force the lens in with too much torque. I've gotten myself so excited I'm going straight to the stores in the morning.

If this works I could mail these to others who want to try them. They could be mailed in an envelope and the envelope would look empty since Mylar is thin and transparent.