CNN  —  In the old photo studios of Lagos, Nigeria, negatives were being burned. No longer needed or wanted, they were too difficult to store, the subjects had moved on or died, and the photo labs that printed them had long since shuttered. Those that were not discarded or set alight were left to degrade in rice bags and cardboard boxes, the humid Lagos air slowly destroying the emulsion. When Karl Ohiri, a British Nigerian artist, first heard about this, he was shocked. “I was witnessing this