OCR vs. Image Embeddings for PDF RAG: Which One is Better? @Weaviate
OCR vs. Image Embeddings for PDF RAG: Which One is Better?  @Weaviate
Uploaded March 2026 | Updated September 2026, 1 hour ago
My colleagues at Weaviate released IRPAPERS, a benchmark comparing ๐—ถ๐—บ๐—ฎ๐—ด๐—ฒ-๐—ฏ๐—ฎ๐˜€๐—ฒ๐—ฑ and ๐˜๐—ฒ๐˜…๐˜-๐—ฏ๐—ฎ๐˜€๐—ฒ๐—ฑ retrieval over 3,230 pages from 166 scientific papers.

The setup: Take the same PDFs and process them two ways. For text, run OCR with GPT-4.1 and embed with Arctic 2.0 + BM25 hybrid search. For images, embed raw page images with ColModernVBERT multi-vector embeddings. Test both on 180 needle-in-the-haystack questions.

๐—ง๐—ต๐—ฒ ๐—ฟ๐—ฒ๐˜€๐˜‚๐—น๐˜๐˜€:

Text edges out images at the top rank: 46% vs 43% Recall@1
But images match or exceed text at deeper recall: 93% vs 91% Recall@20

But text and image based methods actually fail on ๐˜ฅ๐˜ช๐˜ง๐˜ง๐˜ฆ๐˜ณ๐˜ฆ๐˜ฏ๐˜ ๐˜ฒ๐˜ถ๐˜ฆ๐˜ณ๐˜ช๐˜ฆ๐˜ด.

At Recall@1:
โ€ข 22 queries succeed with text but fail with images
โ€ข 18 queries succeed with images but fail with text

This complementarity is what makes ๐— ๐˜‚๐—น๐˜๐—ถ๐—บ๐—ผ๐—ฑ๐—ฎ๐—น ๐—›๐˜†๐—ฏ๐—ฟ๐—ถ๐—ฑ ๐—ฆ๐—ฒ๐—ฎ๐—ฟ๐—ฐ๐—ต work. By fusing scores from both text and image retrieval, they achieved:
โ€ข 49% Recall@1 (beating either modality alone)
โ€ข 81% Recall@5
โ€ข 95% Recall@20

00:00 - Intro
00:08 - Visual- vs Text-based methods
01:04 - The IRPapers dataset
01:59 - The 6 different search strategies
03:43 - The results
04:30 - The paper's most interesting finding...
05:11 - Conclusion
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OCR vs. Image Embeddings for PDF RAG: Which One is Better?

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