I am trying to understand how specular highlights work. As I understand specular highlights are created by reflecting light-sources in a mirror-like fashion. Because faraway reflected objects are out of focus when focusing on a mirror surface, analogously I expect that specular highlights will be out of focus when focusing on an object surface. To test this out I did a "human eye" test. I looked at a close by wine bottle with my eyes and I can clearly focus either on the specular highlights or glass surface, but not both, so I surmise that understanding specular highlights as an imperfect mirror reflection seems to work.
Despite this I don't see blurry (out of focus) specular highlights when focusing on nearby objects. As a quick illustration see this image where the object camera distance seems to affect the blur of the specular highlights much more than the camera light-source distance, as evidenced by the greater blur of the specular highlights on the left apple then the right apple.
Why is this? Is there any way that a specular highlight is more "in focus" than the object surface it is reflecting off of (analogously to focusing on a light-source in the mirror)?
I am thinking of a couple explanations:
this might be due to the convex surface of objects like apples or wine bottles, as I noticed that photographs of reflections in sunglasses have both the glasses and reflections mostly sharp, but this doesn't explain why the same effect is seen on water surfaces, which are approximately flat and as well as contradictory evidence from the "human eye" test.
maybe this is an illusion due to the object surface structure being the main contributing factor to the apparent sharpness of specular highlights, but I am seriously unconvinced based on the "human eye" test and also observing the same effect on glass surfaces that should sufficiently smooth.