content: It's a little more than that. Comparatively, the foreground is so much brighter that the exposure time needs to be short... so short that the light from objects that aren't quite as bright don't show up. This is a result of the film or sensor's inability to pick up dimmer light sources is known as "reciprocity failure." Although the term originally referred to classic film, we have somewhat similar issues with digital sensors. To offset these shortfalls in film and digital sensors, you can either lower the ISO of the medium and take longer exposures (causing reciprocity failure) or crank up the ISO (causing noise in both mediums). https://filmphotographyproject.com/content/howto/2011/10/what-reciprocity-failure/