Following from the idea of underexposing from my previous entry, I decided to take a series of shots under natural light (both on overcast and sunny days), as well as combining natural and artificial light. Some of these shots are shown and discussed below.
The first shot was taken indoors, in a corridor which is lit with a combination of artificial and natural light (from openings in the ceiling). There is a very subtle colour cast on this shot which I find quite attractive. The top end of the light strip has a bluish tone coming from the natural light, which is partially diffused through glass panels, which may further cool its tonality, whereas the bottom half of the strip has a slightly warmer tone, coming from the less intense artificial lamps, with incandescent bulbs, fixed to the ceiling. I initially had though about converting this picture into black and white, to emphasize the shapes and the contrast of the light, but I decided against it in the end because the subtle colour hues of the light would be lost with this.
The next shot was taken outdoors with only natural light. It was sunny, and consequently, the light had a slight golden colour cast. Exposure was set not to blow the highlights, creating a nice, soft graduation from dark to light gray (the light was coming from under some arches, hence the shadows on the left). While I like the overall look of the picture, it does lack the hue variation of the previous one due to the single light source.
The last shot in the series combines again both natural and artificial light, but this time there is a combination of direct and reflected / diffused light. There is also a clear distinction between the sections of the frame which are illuminated by the different sources, so that there is almost no spill or mixture like in the first shot. With each light source having its distinct colour temperature, the result is a picture of parts that cannot be separated but complement each other and allow the view to wonder from one segment to the next and back. I find it quite pleasant to look, if it was not for the slightly irritating bit of dull highlight at the bottom (water reflection at the corner of the wall), which could be corrected in post-processing, but I am showing here for completeness.