Sketchbook IV (Frequencies (Double Take)), 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.
- First printing, 500 numbered copies
- June 2022
- Hardcover, 11 × 9 1/2 inches
- 84 pages
- Printed by Pureprint, London, U.K.