Generative vision-language models (VLMs) exhibit strong high-level image understanding but lack spatially dense alignment between vision and language modalities, as our findings indicate. Orthogonal to advancements in generative VLMs, another line of research has focused on representation learning for vision-language alignment, targeting zero-shot inference for dense tasks like segmentation. In this work, we bridge these two directions by densely aligning images with synthetic descriptions generated by VLMs. Synthetic captions are inexpensive, scalable, and easy to generate, making them an excellent source of high-level semantic understanding for dense alignment methods. Empirically, our approach outperforms prior work on standard zero-shot open-vocabulary segmentation benchmarks/datasets, while also being more data-efficient.
@article{arxiv.2509.11840,
title = {Synthetic Captions for Open-Vocabulary Zero-Shot Segmentation},
author = {Tim Lebailly and Vijay Veerabadran and Satwik Kottur and Karl Ridgeway and Michael Louis Iuzzolino},
journal= {arXiv preprint arXiv:2509.11840},
year = {2025}
}