The image below shows Rachmaninoff's Prelude in G minor, Op. 23, No. 5, measure 43 (IMSLP). The treble staff is in 4:4; however, the bass staff has 24 sixteenth notes in it, and though not marked, these are probably meant to be arranged into triplets: every three sixteenth notes fit into the space of two sixteenth notes from the treble staff. Sixteenth notes in the bass staff are therefore shorter than sixteenth notes in the treble staff, and the same goes for eighth notes, etc.
The question is this: the marked note in the middle of the treble staff is linked to a note from the bass staff. What length does that note have? Does it have the length of an eighth note from the treble staff (half a beat), or the length of an eighth note from the bass staff (a third of a beat)? And offset to which note is it played? In other words, does it belong conceptually in the bass staff?
I would go further and actually ask: are there two superimposed F# notes in the bass staff? A sixteenth and an eighth? And what's that eighth doing there? Which staff does it belong to?