Inktense Brown vs Ink Black

How close are they?

ΔE 20.3, loose: different enough that you should pick on purpose. Ink Black is noticeably darker, more muted than Inktense Brown.

Can I use Ink Black instead of Inktense Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Ink Black is noticeably darker, more muted than Inktense Brown.

Can I use Inktense Brown instead of Ink Black?

The same difference applies the other way round: Inktense Brown is noticeably lighter, more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.