SpyderCube
SpyderCube is a color target for color balance and exposure adjustment in photo and video production.
Design
SpyderCube is a specially colored cube, standing on one of its vertices. It has a chrome ball on the top vertex and a hole in one of the faces. It also has a rope on the top vertex and the tripod thread on the bottom one, so it can be mounted.
Three of its faces are usually directed to the photographer. Two of them are split into white and grey triangles. The other one is colored black. It has a hole that appears darker in the image[1] and can be used for a better black level estimation.
The chrome ball on the upper vertex shows the reflection of the scene. So it can be used in postprocessing to estimate the quantity and types of light sources that illuminate the scene.
Features
Grey and white triangles are achromatic with an almost constant spectrum in the visible range, which allows the use of SpyderCube to estimate illumination. Two colors enable estimation in different exposure conditions. On brightly illuminated images, the white triangles may have clipped areas that cannot be used properly. Conversely, the chromaticity of grey triangles in darker images can be unstable due to black level noise[2].
The scene may be illuminated by several light sources, not a single one. Two faces allow two illumination estimations, which is not possible in flat color targets such as commonly used ColorChecker or Gray card. Another volumetric color object is the GreyBall used in some data sets[3][4], which can be theoretically used to estimate an unbounded count of light sources. Black and white faces may be used to adjust the contrast range[5].
SpyderCube is used in some data sets[6][7][8] for ground truth estimation.
See also
References
- ↑ Brennesholtz, Matthew (2017-04-19). "Cinematography, HDR and Waveform Monitors". DisplayDaily. Retrieved 2021-03-12.
- ↑ Ershov, E.; Savchik, A.; Semenkov, I.; Banić, N.; Belokopytov, A.; Senshina, D.; Koščević, K.; Subašić, M.; Lončarić, S. (2020). "The Cube++ Illumination Estimation Dataset". IEEE Access. 8: 227511–227527. arXiv:2011.10028. doi:10.1109/ACCESS.2020.3045066. ISSN 2169-3536. Unknown parameter
|s2cid=ignored (help) - ↑ Ciurea, Florian; Funt, Brian (2003-01-01). "A Large Image Database for Color Constancy Research". Color and Imaging Conference. 2003 (1): 160–164.
- ↑ Aghaei, Hoda; Funt, Brian (2020-09-01). "A Flying Gray Ball Multi-illuminant Image Dataset for Color Research". Journal of Imaging Science and Technology. 64 (5): 50411–1–50411-8. doi:10.2352/J.ImagingSci.Technol.2020.64.5.050411.
- ↑ "Manufacturer manual" (PDF). Unknown parameter
|url-status=ignored (help) - ↑ "Color constancy - Image Processing Group". ipg.fer.hr. Retrieved 2021-03-12.
- ↑ Qian, Yanlin; Käpylä, Jani; Kämäräinen, Joni-Kristian; Koskinen, Samu; Matas, Jiri (2020-03-08). "A Benchmark for Temporal Color Constancy". arXiv:2003.03763 [cs.CV].
- ↑ Visillect/CubePlusPlus, Visillect, 2021-03-12, retrieved 2021-03-20
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