If you take pictures and the aperture settings are not ideal, you will see a light shadow in the corners.
This effect is a sign of bad quality, but is also often used as a design element in movies, pictures and so on – how is it called?
I want to use it, but I have no clue how it’s called.
It is called Vignetting, which, as you described:
[…] is a reduction of an image’s brightness or saturation at the periphery compared to the image center.
It can appear as
- Mechanical (filters used in a shoot, improper lens hood, etc)
- Optical (lens)
- Natural (illumination falloff)
- Pixel (digital sensor’s alignment to the scene)
- Photographic film (the film’s properties)
Nowadays it can be easily done in post-processing.