# When to Freeze the Vision Tower? — Probing Lab + Downstream Eval

> Source: https://sukruyusufkaya.com/en/learn/fine-tuning-cookbook/ftc-vision-tower-freeze-probing
> Updated: 2026-05-14T14:42:54.344Z
> Category: Fine-Tuning Cookbook (Model-by-Model)
> Module: Part VI — Vision-Language Multimodal FT
**TLDR:** VLM FT's most debated decision: freeze the vision encoder or not? Frozen → vision capability preserved, training fast, less risk. Unfrozen → +2-5% quality but 3-5x slower training + overfit risk. Ablation: 5 freeze strategies comparison, RTX 4090 + Qwen 2.5-VL 7B.