Before the invention of photographic processes there was no way to preserve the images produced by these cameras apart from manually tracing them. The earliest cameras were room-sized, with space for one or more people inside; these gradually evolved into more and more compact models. By Niépce's time portable box camerae obscurae suitable for photography were readily available. The first camera that was small and portable enough to be practical for photography was envisioned by Johann Zahn in 1685, though it would be almost 150 years before such an application was possible.