Adapting Visual Category Models to New Domains
Kate SaenkoBrian KulisMario FritzTrevor Darrell
Proposes a metric learning framework for visual domain adaptation that aligns feature distributions using cross-domain pairwise constraints and introduces the multi-domain Office benchmark dataset to evaluate object recognition across disparate imaging conditions.
Object recognition systems trained on large labeled image collections often fail when applied to images from new cameras, lighting conditions, or environments, because the underlying feature distributions change. This domain shift limits practical use in settings such as robotics, where labeled data for every new sensor or scene is scarce.
The work set out to develop and test a general method that learns a transformation mapping features from a source domain closer to those of a target domain, allowing classifiers trained on abundant source labels to perform well in the target domain even when few or no target labels exist for some categories.
The authors created a new benchmark dataset containing the same 31 object categories imaged in three distinct domains—web photographs, high-resolution DSLR images, and low-resolution webcam images—plus instance-level subsets. They formulated domain adaptation as the problem of learning a regularized linear or kernelized transformation from labeled pairs of similar and dissimilar cross-domain examples, then applied the resulting distance function inside a nearest-neighbor classifier. Experiments compared the approach against unadapted baselines and standard metric-learning methods across multiple source–target pairs and two settings: categories seen during adaptation and entirely new categories.
The learned transformation raised classification accuracy in every tested shift. Gains were largest for the most severe shift (web to webcam), where performance roughly doubled relative to the unadapted baseline. The method also improved accuracy on categories never labeled in the target domain, and the asymmetric variant outperformed the symmetric one when domain differences were large. Standard metric learning applied to pooled data performed worse than the domain-specific constraints used here.
These results show that a modest number of cross-domain labeled pairs can recover enough of the domain shift to make existing object models usable in new imaging conditions without collecting target labels for every category. The technique therefore reduces the labeling burden that currently prevents large public datasets from being deployed on robots or other specialized platforms.
Further gains are likely from richer constraint sets, automatic selection of which source categories to use for learning the transform, and integration with classifiers beyond nearest neighbors. The main limitations are reliance on at least some target-domain labels to build the transformation, restriction of the symmetric version to equal-dimensional features, and evaluation on only one classifier and one dataset; results should therefore be confirmed on additional domains and tasks before broad deployment.
- Paper: A theory of learning from different domains, Shai Ben-David et al. (2010). This foundational theoretical study on domain adaptation provides the generalization bounds and divergence measures that motivate transform-based feature alignment.
- Paper: Unsupervised Domain Adaptation by Backpropagation, Yaroslav Ganin et al. (2015). This work extends early explicit domain transformation techniques into an end-to-end adversarial framework using gradient reversal layers for deep networks.
- Paper: Adversarial Discriminative Domain Adaptation, Eric Tzeng et al. (2017). This paper builds directly upon transfer methodologies by introducing Adversarial Discriminative Domain Adaptation to align source and target feature spaces.
