- 11 × 9 ½ inches (27.9 × 24.1 cm), Portrait
- Hardcover, 84 pages
- First printing: June 2022, 500 numbered copies
- Printed by Pureprint, U.K.
Sketchbook IV (Frequencies (Double Take)) is the fourth installment of Ackermann's sketchbook series. Begun in March of 2020, this sketchbook was revisited, rethought, gaining the title Double Take: a delayed reaction to something unexpected, immediately after one's first reaction.