This idea actually very well explains why those light paintings are usually created at night times and we cannot see the person holding the light source in the picture: during night times sunlight intensity reduces, and the irradiance of any artificial light source becomes much stronger comparing to, say the clothes of the person who's holding the light source and moving around during the exposure time. The long exposure time with the strong irradiance of the source thus is much more visible than the less illuminated person/backgrounds. For reference, an awesome site about light paintings: https://lightpaintingbrushes.com/pages/light-painting-tutorials.
xiaoyankang
Here's an interesting journal describing an exposure renderer.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038586
This idea actually very well explains why those light paintings are usually created at night times and we cannot see the person holding the light source in the picture: during night times sunlight intensity reduces, and the irradiance of any artificial light source becomes much stronger comparing to, say the clothes of the person who's holding the light source and moving around during the exposure time. The long exposure time with the strong irradiance of the source thus is much more visible than the less illuminated person/backgrounds. For reference, an awesome site about light paintings: https://lightpaintingbrushes.com/pages/light-painting-tutorials.
Here's an interesting journal describing an exposure renderer. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038586