To my surprise, the photos taken with the 5MP camera were substantially better than the ones from the 8MP camera.
I used Photoscan (Photogrammetry software) to render a 3D model from images taken from both cameras, the resulting model was pretty bad.
IMAGEN DE PHOTOSCAN
MODELO DE PHOTOSCAN
The 3D models from each set of images were quite bad. My first guess
I saw a tutorial that encouraged me to manually fix the focus for the 8MP camera and the next photographs were much better than the ones taken with the 5MP camera.
At this point I started to think that the first experiment went wrong not only because of the image quality but also from the camera setup, in my past photogrammetry projects, I always held the camera in my hand whilst moving around the object and in that case, elements from the background were essential to help Photoscan build the 3D meshes. The new setup works in a very different way as you actually need to remove all the background from the images (I did it using masks) but perhaps I just need to do more testing to learn more about how to do this other process using Photoscan.
A have been also doing more research on how to build a proper photogrammetry boot and I already know you could potentially connect 8 Raspberry Pi cameras onto a single Raspberry Pi board. Having an array of cameras pointing at the object from 8 different angles will make the process go much faster. I also plan to build a 3D printed Arduino controlled platform for a fully automated process with a budget under £350.
So now I am focused on getting the funding to create the Photogrammetry booth and to continue my research.