A second-order theory of texture for depth from focus

Sreekar Ranganathan, Ioannis Gkioulekas

ECCV 2026

teaser
Computer vision traditionally considers depth recovery of scenes with sparse texture features impossible with passive methods such as depth from focus (top). We show that simply adding a narrowband spectral filter to the camera makes passive depth recovery of such scenes possible (bottom). We explain this surprising finding by developing a theory of second-order texture—a form of subjective speckle whose in-focus contrast is enhanced with decreasing spectral bandwidth (crops to the left).

Abstract

We present a theory of textured appearance of optically rough surfaces based on wave optics, emphasizing the role of texture for passive depth from focus. Our theory shows that even surfaces that traditional computer vision would consider textureless can produce textured appearance, due to subjective speckle from surface microgeometry. We analyze the properties of this second-order texture, and show that we can enhance its contrast under natural ambient lighting by simply using a narrowband spectral filter. Doing so results in dramatic improvements in passive depth reconstruction of seemingly textureless scenes, as we demonstrate through extensive theory, simulations, and real-world experiments.

Robustness to illumination conditions

illumination
We demonstrate fine-scale depth recovery of objects with sparse texture features under ambient lighting indoors (ceiling lights, left) and outdoors (sunlight, right). In both cases, adding a spectral filter dramatically improves DFF performance.

Robustness to underexposure conditions

snr
Using a spectral filter improves DFF even at suboptimal exposures. At 1/4 the optimal exposure time, second-order texture is already discernible from noise, improving focus measures and DFF performance.

Visualization

Visualizations of all our experimental results are available at the interactive supplemental website.

scene
no filter 10 nm filter
no filter 10 nm filter

Resources

Paper: Our paper and supplement are available here.

Code: Our code will be available soon.

Data: Our data will be available soon.

Citation

@InProceedings{Ranganathan:SOT:2026,
	author    = {Ranganathan, Sreekar and Gkioulekas, Ioannis},
	title     = {A second-order theory of texture for depth from focus},
	booktitle = {European Conference on Computer Vision (ECCV)},
	year      = {2026},
	pages     = {1--10},
	publisher = {Springer},
	year      = {2026},
}

Acknowledgments

We thank Dorian Chan, Aswin Sankaranarayanan, and Matthew O'Toole for helpful discussions about speckle, and Mian Wei for feedback on writing. This work was supported by NSF award 2047341, and a Sloan Research Fellowship.