This methodology of taking an electrophotography is also known as CONTACT ELECTROPHOTOGRAPHY because we use no camera at all and the object is in contact with the film.

The emulsion side of the film is always held upwards, in contact with the finger!

This type of electrode is quite simple:

just a printed circuit board, the way it comes when you buy it at your electronics' store.

Of course you'll want to register your images, therefore we put a photographic film between the finger and the base (dielectric plate) of the PC board...

As you may see in the schematic above, the streamers appear between the finger and the film surface. Light from these streamers forms the image over the film.

But this methodology uses the film in a very unusual way (contact methodology), and the film manufacturer certainly did not design it to be used this way...
Keeping in mind this unusual usage of the film, there's always the possibility of formation of streamers beneath the film thus activating the lower red sensitive layer of the color film and producing false images...

A sophisticated electrode with a film spool, exposition counter and film driving mechanism is depicted below:

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