I'm not sure if there's solid rules about it or not. I think it depends on if it works or not. My personal opinion, and that's all it is, is that it's overdone. More often it seems distracting, making you want to tilt your head to view the image. There has been images where it has worked, added something. But again, my opinion only, more often it hasn't, especially landscapes, sunsets, etc.
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