The signal is typically bandlimited by hardware — the optics and sensor. When it's not, you get weird effects, though that's rare because cameras have optical low pass filters to avoid this.

When they don't, like the Canon 5D mark ii when used in video mode (which just threw out most of the sensor's pixels to get to 1080p), you get aliasing producing moire patterns like this:

https://youtu.be/dMHDB5fG6ys?t=218