May inherit biases from the base SigLIP model and training data
Not suitable for tasks requiring detailed fine-grained recognition without further training
Trained on surveillance data; suitable for tasks where a substantial portion of the person is visible

Training

Loss function

Type: Soft contrastive loss with label smoothing; image-to-image contrastive loss for same-identity image pairs.
Description: The model is trained to align text and image embeddings using a modified contrastive objective. Instead of relying on hard one-hot targets, label smoothing allocates a small probability mass to all other samples in the batch. All embeddings are normalized prior to similarity computation, and the loss is applied symmetrically in both the image-to-text and text-to-image directions. To encourage re-identification and emphasize clothing features rather than pose or background, an additional image-to-image contrastive loss is incorporated.

Evaluation Metrics

Truncated Cumulative Matching Characteristic (CMC) AUC
- Measures the fraction of queries where the correct match appears within the top K ranks (e.g., top-10). Unlike MRR or strict top-1 accuracy, this metric rewards consistent retrieval of all relevant matches near the top ranks, rather than a few perfect hits with others ranked very low.

Datasets

Sources: CUHK-PEDES, ICFG-PEDES, IIITD, ITCPR, PRW-TBPS, PETA, (part of SYNTH and RSTPReid for testing)
Processing: Text descriptions were processed with the Mistral LLM to remove ambiguous information about pose or context, leaving only clear visual characteristics in a structured format, where key features are separated with comma. During train/val/test the original splits are respected as much as possible.

The splits are created as follows:

CUHK-PEDES: test: 1000 identities following the original split; validation: 150 identities sampled from the original validation split; train: all remaining identities
ICFG-PEDES: test: 946 identities following the original split; validation: 150 identities sampled from the original training split; train: all remaining identities
IIITD: test: 2500 identities following the original split; validation: 150 identities sampled from the original validation split; train: all remaining identities
ITCPR: Originally designed for zero-shot evaluation, so a new split is created:test: 1000 randomly selected identities; validation: 150 randomly selected identities; train: all remaining identities
PRW: test: 450 identities following the original split; validation: 150 identities sampled from the original training split; train: all remaining identities
PETA: The original random image-level split can cause identity leakage. Therefore, the identity-based split from PETA-ZS is adopted: test: 1706 identities following the original split; validation: 150 identities sampled from the original validation split; train: all remaining identities
RSTPReid: Only the 200 test images are used for evaluation due to annotation errors in the rest of the dataset.
SYNTH: 1000 random images are used for the test set because the generated captions are noisy and sometimes inaccurate.

Training Setup

Frozen model head initially; only heads were trained.
Fine-tuning: later trained the whole model.
Optimizer: AdamW
Learning rate: 1e-4 for warm-up, 5e-6 for the rest
Epochs: 4 epochs for model head fine-tuning, and 50 epochs for full model fine-tuning
Visual Augmentations: random operations including small rotations, scale, hue variations, horizontal flip, and color jitter
Text Augmentations: random subsets of key features are selected and removed from the comma-separated description strings to create augmented training samples
Training Codes: codes are available on [github] (https://github.com/MarketaJu/ReducedSiglipForPersonDescription)
Package Versions: torch==2.9.1, transformers==4.57.3, pillow==12.0.0, torchvision==0.24.1

Results

The model is evaluated on data mentioned above. The following table summarizes the number of identities, images, and queries for each subset.
The final test set is a merge of all subsets.

Dataset	#Identities	#Images	#Queries
CUHK	1000	3074	6156
ICFG	946	19848	19873
IIITD	2500	2500	5000
ITCPR	1000	1620	1620
PRW	450	2057	4114
PETA	1706	3933	4614
RSTPReid	200	1000	1932
SYNTH	1000	1000	1000
Final (All)	8802	35032	44309

Evaluation of the Model on Text-based Image Retrieval Task

Since the task is focused on retrieving the correct person identity rather than the exact matching image, the evaluation is performed as follows:

For each text query, the goal is to retrieve the correct identity, not the exact corresponding image.
During evaluation, scores are computed over all images belonging to the same identity, and the maximum score is taken to represent that identity.
These identity-level scores are then ranked, and the following retrieval metrics are calculated:
- Top-k: standard top-1, top-5, top-10 accuracy
- MRR: Mean Reciprocal Rank
- CMC AUC: Truncated CMC AUC evaluated up to rank 20

Dataset	Top-1	Top-5	Top-10	MRR	CMC AUC (20)
CUHK	66.2	87.5	92.7	74.1	91.5
ICFG	52.9	76.6	83.8	61.1	82.8
IIITD	68.4	89.2	93.7	77.8	92.7
ITCPR	42.7	68.6	78.9	52.0	78.0
PRW	60.5	84.9	91.6	69.9	90.5
PETA	44.8	74.3	83.7	56.8	82.2
RSTPReid	50.5	78.5	86.2	60.9	85.3
SYNTH	47.2	72.5	81.9	58.9	80.9
Final (All)	51.5	74.9	82.3	60.4	81.3

Cross-Model Comparison

Model Variant	Top-1	Top-5	Top-10	MRR	CMC AUC (20)
google/siglip-base-patch16-224	16.4	33.1	41.4	23.8	41.1
google/siglip2-base-patch16-224	12.3	26.3	34.2	18.7	34.2
finetuned_siglip2	53.8	77.0	83.8	62.6	82.8
finetuned_siglip2_reid	51.5	74.9	82.3	60.4	81.3
siglip2-person-description-128	51.0	75.0	82.4	60.4	81.4
siglip2-person-description-64	49.0	73.8	81.7	58.6	80.5
siglip2-person-description-32	43.1	70.0	78.2	53.5	77.3

Evaluation of the Model on Image Reidentification Task

Since some images from Market-1501 are also included in the aforementioned datasets used for training, the reported results on this dataset are not objective. Reported metrics are Top-1/5/10 and mAP.

Model Variant	Market 1501	MSMT17	Duke MTMC	EntireID
google/siglip-base-patch16-224	20.3 / 36.2 / 43.3	60.3 / 73.1 / 77.5	60.8 / 75.1 / 79.5	30.0 / 45.5 / 51.9
google/siglip2-base-patch16-224	22.9 / 38.0 / 45.9	59.1 / 71.3 / 76.2	60.2 / 74.2 / 78.7	32.3 / 47.1 / 54.0
finetuned_siglip2	86.8 / 94.7 / 96.4	87.8 / 93.0 / 94.5	91.1 / 95.3 / 96.4	73.5 / 86.0 / 89.5
finetuned_siglip2_reid	90.7 / 97.0 / 98.4	92.8 / 96.4 / 97.2	92.7 / 96.2 / 97.0	79.3 / 89.8 / 92.1
siglip-person-description-64	86.0 / 93.9 / 96.2	84.6 / 91.0 / 92.8	89.8 / 94.8 / 95.7	68.3 / 82.4 / 86.3
siglip2-person-description-64	87.1 / 95.1 / 96.5	84.4 / 90.9 / 92.9	89.0 / 94.4 / 95.6	68.0 / 83.0 / 86.9

Model Variant	Market 1501	MSMT17	Duke MTMC	EntireID
google/siglip-base-patch16-224	6.4	13.2	17.5	16.1
google/siglip2-base-patch16-224	7.5	12.0	17.0	17.2
finetuned_siglip2	73.5	48.7	60.6	54.4
finetuned_siglip2_reid	81.0	66.6	66.8	60.6
siglip-person-description-64	72.3	44.0	57.1	48.9
siglip2-person-description-64	73.4	44.1	57.0	49.8

Usage

The usage is identical to SigLIP.

python

# Import custom model code from repository
from modeling_resipvd import ReSiPVDModel

# Load the model from Hugging Face Hub
processor = AutoProcessor.from_pretrained("google/siglip2-base-patch16-224")
model = AutoModel.from_pretrained("MarketaJu/siglip2-person-description-reid")

# Example: get embeddings
from skimage.io import imread
image = imread("test.jpg")
text_inputs = processor(text=["random person description"], return_tensors="pt", padding="max_length", max_length=64, truncation=True)
image_inputs = processor(images=image, return_tensors="pt", padding="max_length", max_length=64, truncation=True)
text_embeds = model.get_text_features(**text_inputs)
image_embeds = model.get_image_features(**image_inputs)


---

## Citation

If you use this model, please cite:

```bibtex
@misc{reduced-siglip-visualdescription,
  title={Reduced SigLIP for Visual Descriptions},
  author={Marketa Jurankova},
  year={2025},
  publisher={Hugging Face},
  howpublished={\url{https://huggingface.co/collections/MarketaJu/reduced-siglip-for-person-visual-description}}
}