1. What ``Sustained Investigation'' Means
The Sustained Investigation (SI) is not a themed series of pretty pictures --- it is documented evidence of an inquiry-based, in-depth study of materials, processes, and ideas developed over the whole course.
You submit exactly 15 digital images for the SI. They can include finished works, sketches, models, plans, diagrams, process shots, and detail images. The College Board's own glossary defines Sustained Investigation as ``an inquiry-based and in-depth study of materials, processes, and ideas over time.''
A Sustained Investigation is not a ``series'' with a pretty visual theme (a leftover concept from the old AP Studio Art Concentration) --- it must be built around a genuine, evolving question, not just a repeated subject or color palette.
Students treat the SI like 15 separate finished artworks. Readers reward inquiry-driven exploration, so a portfolio of 15 polished-but-unrelated ``masterpieces'' scores lower than 15 images showing one real investigation, warts and all.
SI $arrow$ 15 images $arrow$ one evolving question, not 15 pretty pictures.