Today I was watching a video on Youtube where I saw lines representing the light of a light source. While the image was downscaled like this:
There were some clear patterns on the horizontal and vertical lines going through the source. I already saw this phenomenon a few times when I received photos of computer monitors. When there were some closely packed lines I saw patterns resembling those in the screenshot when I was playing around with she scale of the image. As I was increasing or decreasing the size of the image the pattern was changing continuously.
This is what the actual image looks like when it isn't scaled down:
The patterns seem to disappear.
What causes this phenomenon? I assumed it was falling under the category optics. If I am false, I am sorry.
source of the video: https://www.youtube.com/watch?v=d-o3eB9sfls
Answer
The moiré fringes are caused by undersampling, it is the difference between properly sampling a small field of view and undersampling a larger field, it causes spatial aliasing.
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