This interests me from a technical point of view. It looks to me as if this was one of the experiments in using high-speed colour negative film instead of the colour transparency film more common for reproduction in those days. Most of the time I’d use Fuji Velvia for the colour saturation, resolution and lack of grain. It was nominally 50ISO but I rated it at 32. This meant the background light indoors scarcely registered, even with very long exposures. Colour print films seemed to offer a better balance of speed/quality so I would sometimes use those to try and get a bit of context into the indoor work. Always interested in the context… Always wanted everyone to feel they had been there at the time…