Penguin-VL: Exploring the Efficiency Limits of VLM with LLM-based Vision Encoders

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Main Authors: Zhang, Boqiang, Ke, Lei, Yang, Ruihan, Gao, Qi, Qu, Tianyuan, Chen, Rossell, Yu, Dong, Leoweiliang
Format: Preprint
Published: 2026
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author Zhang, Boqiang
Ke, Lei
Yang, Ruihan
Gao, Qi
Qu, Tianyuan
Chen, Rossell
Yu, Dong
Leoweiliang
author_facet Zhang, Boqiang
Ke, Lei
Yang, Ruihan
Gao, Qi
Qu, Tianyuan
Chen, Rossell
Yu, Dong
Leoweiliang
contents Vision Language Model (VLM) development has largely relied on scaling model size, which hinders deployment on compute-constrained mobile and edge devices such as smartphones and robots. In this work, we explore the performance limits of compact (e.g., 2B and 8B) VLMs. We challenge the prevailing practice that state-of-the-art VLMs must rely on vision encoders initialized via massive contrastive pretraining (e.g., CLIP/SigLIP). We identify an objective mismatch: contrastive learning, optimized for discrimination, enforces coarse and category-level invariances that suppress fine-grained visual cues needed for dense captioning and complex VLM reasoning. To address this issue, we present Penguin-VL, whose vision encoder is initialized from a text-only LLM. Our experiments reveal that Penguin-Encoder serves as a superior alternative to traditional contrastive pretraining, unlocking a higher degree of visual fidelity and data efficiency for multimodal understanding. Across various image and video benchmarks, Penguin-VL achieves performance comparable to leading VLMs (e.g., Qwen3-VL) in mathematical reasoning and surpasses them in tasks such as document understanding, visual knowledge, and multi-perspective video understanding. Notably, these gains are achieved with a lightweight architecture, demonstrating that improved visual representation rather than model scaling is the primary driver of performance. Our ablations show that Penguin-Encoder consistently outperforms contrastive-pretrained encoders, preserving fine-grained spatial and temporal cues that are critical for dense perception and complex reasoning. This makes it a strong drop-in alternative for compute-efficient VLMs and enables high performance in resource-constrained settings. Code: https://github.com/tencent-ailab/Penguin-VL
format Preprint
id arxiv_https___arxiv_org_abs_2603_06569
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Penguin-VL: Exploring the Efficiency Limits of VLM with LLM-based Vision Encoders
Zhang, Boqiang
Ke, Lei
Yang, Ruihan
Gao, Qi
Qu, Tianyuan
Chen, Rossell
Yu, Dong
Leoweiliang
Computer Vision and Pattern Recognition
Vision Language Model (VLM) development has largely relied on scaling model size, which hinders deployment on compute-constrained mobile and edge devices such as smartphones and robots. In this work, we explore the performance limits of compact (e.g., 2B and 8B) VLMs. We challenge the prevailing practice that state-of-the-art VLMs must rely on vision encoders initialized via massive contrastive pretraining (e.g., CLIP/SigLIP). We identify an objective mismatch: contrastive learning, optimized for discrimination, enforces coarse and category-level invariances that suppress fine-grained visual cues needed for dense captioning and complex VLM reasoning. To address this issue, we present Penguin-VL, whose vision encoder is initialized from a text-only LLM. Our experiments reveal that Penguin-Encoder serves as a superior alternative to traditional contrastive pretraining, unlocking a higher degree of visual fidelity and data efficiency for multimodal understanding. Across various image and video benchmarks, Penguin-VL achieves performance comparable to leading VLMs (e.g., Qwen3-VL) in mathematical reasoning and surpasses them in tasks such as document understanding, visual knowledge, and multi-perspective video understanding. Notably, these gains are achieved with a lightweight architecture, demonstrating that improved visual representation rather than model scaling is the primary driver of performance. Our ablations show that Penguin-Encoder consistently outperforms contrastive-pretrained encoders, preserving fine-grained spatial and temporal cues that are critical for dense perception and complex reasoning. This makes it a strong drop-in alternative for compute-efficient VLMs and enables high performance in resource-constrained settings. Code: https://github.com/tencent-ailab/Penguin-VL
title Penguin-VL: Exploring the Efficiency Limits of VLM with LLM-based Vision Encoders
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2603.06569