I'm with you on this - I don't know anything about photography, but I do know I would like the images to be better. If I move the piston to the bottom, and put the camera all the way down, I get a better image of the valves, but still not as good as a close up picture with my iphone. Seems that there is room for improvement. The borescopes with multiple cameras look interesting - not sure if they can look all the way back to the valves.I have the Vividia, and although it works, I am going to keep looking. There are more than mega pixels to consider. The key limitation to it is optical, namely the local length. It is marginal at 3" but 2" or less and it is fuzzy. If someone was handy in optics and could change the focal length then it would be converted to an outstanding device for bore and valve inspection.
I suspect since the dental cameras are shorter focal length they make some good close up pictures.