I designed and built a Canon EF Mount for my Game Boy Camera. The GBC has a sensor size of about 3.6mm² which seems equivalent to a 1/4" sensor (Wikipedia). This gives the GBC a crop factor of about 10.81. With my 70-200 f4 mounted on a 1.4x extender, this gives me a max equivalent focal distance of about 200x1.4x10.81=3,026.8mm.

The lens adapter was designed in Rhinoceros 3D and printer on a Monoprice Select Mini v2 in black PLA at a pretty rough layer height (for speed). Minimal supports and cleanup are required to make the lens fit semi-snugly. The GBC sensor PCB screws into the back of the 3D print and with a little cutting and filing, the whole things mounts onto the partly-disassembled GBC, all with the original hardware. If there is enough interest, I might make some modifications to the 3D model and post it on Thingiverse for others to print and experiment with.

I took my abomination out for a walk to the beach to shoot some nature and wildlife. (see gallery below.)