These are scans of some film that I shot a while ago. The "scanner" was my 7D. I clipped the negative sleeve to a lamp that has a white diffused plastic shade. I then adjusted the white balance to match the very yellow-orange incandescent light. The result is better than the last poor scan I did, but it might be time to break down and buy a real scanner with negative scanning capability.

This image is a very poor scan of a negative done on my home flatbed scanner with the ambient light backlighting the image. The negative is far more smooth and detailed. I tried a variety of hacks to get it to work and I found a combination  of things that would allow me to scan the image albeit with a granularity that would be at home in an Instagram photo.