Inktense Black vs Smoke Ink

How close are they?

ΔE 30.4, loose: different enough that you should pick on purpose. Smoke Ink is noticeably lighter, more saturated than Inktense Black.

Can I use Smoke Ink instead of Inktense Black?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Smoke Ink is noticeably lighter, more saturated than Inktense Black.

Can I use Inktense Black instead of Smoke Ink?

The same difference applies the other way round: Inktense Black is noticeably darker, more muted.

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.