English summary below
Fish images (cell phone) from the entrance garden, here:
Video about the construction of a GoPro Hero2 close-up adaptor.
GoPro Hero2 cameras do not have focus mechanism. Having a very wide angle lens they focus anything from infinity to a couple hundred inch.
I needed something able to focus maximum 20 inch (and below that) maximum distance from camera. Indeed I needed something like a convergent lens of about 2 dioptre.
I had already ordered a set of adaptors ...
58mm Macro Close-Up Lens Filter Set +1 +2 +4 +10 With Pouch For Canon DSLR SM | eBay
... but I didn't want to wait any longer (things take more than one month to arrive from China to Portugal) so I decided to try to use what I had already here.
After having disassembled several adaptors trying to find the proper optic element, I finally choose an internal element of a damaged zoom lens whose camera crashed into the ground damaging the lens (permanently locked).
After having assembled the lens element in the plastic adaptor, the focus become operative between about 20inch and 4 inch.
From then on and until today, all videos were recorded using that adaptor.
Regards to everyone and thanks for support