Frames drop when instant mining close to a light source. The particles that are displayed when you brake a block appear black like they have no lighting at first then it is corrected. The surrounding blocks have the same problem, the newly exposed sides appear black then they turn to the correct lighting level.

A similar thing happens when mining in total darkness, the dropped items spawn completely white then turn to the correct lighting level, there is also no noticeable lag when mining in absence of lightning sources.