Polar bear cub, late evening light.
While it can be easily argued that most of the best photos have defined and dramatic light, the new high ISO performance of today’s digital SLR’s have produced a whole new genre of low-light images that simply could not be captured previously. Certainly not in the same quality league. In this frame of a young polar bear cub walking on the snow, of course it would have been wonderful to have a blast of sunshine, but it was mostly cloudy and getting dark (much darker than this frame actually looks). The tiny bit of sun, already set, cast a little pink alpenglow on the distant clouds, offering a very soft and gentle color palette. The camera settings here were on the margin, with motion and a 1/320 second shutter speed, ISO 800. The 1D Mark IV could have probably handled this at 1200 or 1600 ISO as well.
Stock photography buyers are not always looking for super strongly lit subjects that may take too much dominance in their design. All of that to say, it can be worth shooting, even when the light is dim.