This may seem like a obvious/basic question, but I am still curious, and I don't know the answer.
There will obviously be a big difference between an image rendered with a single sample and one rendered with 500 samples, but there will be a smaller difference between an image rendered with 1000 samples and 1500 samples.
What is the technical reason for this?
From what I understand of how cycles works, it fires one ray per pixel from the camera, which bounces and translates through objects at random angles.
It would make sense that samples would bounce in directions that have already been sampled, but I would think it would be possible to skip sampling "duplicate samples" by skipping bounces that are at a similar angle to previous bounces?