Imaging in low light is problematic as sensor noise can dominate imagery, and increasing illumination or aperture size is not always effective or practical. Computational photography offers a promising solution in the form of the light field camera, which by capturing redundant information offers an opportunity for elegant noise rejection. We show that the light field of a Lambertian scene has a 4D hyperfan-shaped frequency-domain region of support at the intersection of a dual-fan and a hypercone. By designing and implementing a filter with appropriately shaped passband we accomplish denoising with a single all-in-focus linear filter. Drawing examples from the Stanford Light Field Archive and images captured using a commercially available lenselet- based plenoptic camera, we demonstrate that the hyperfan outperforms competing methods including synthetic focus, fan-shaped antialiasing filters, and a range of modern nonlinear image and video denoising techniques. We show the hyperfan preserves depth of field, making it a single-step all-in-focus denoising filter suitable for general-purpose light field rendering. We include results for different noise types and levels, over a variety of metrics, and in real-world scenarios. Finally, we show that the hyperfan’s performance scales with aperture count.
The spectral response function of a camera maps the relative sensitivity of the camera imaging system as a function
of the wavelength of the light. The spectral response function of the colour channels of a commercial-off-the-shelf
(COTS) Red/Green/Blue (RGB) camera is often unknown and not typically provided by the manufacturer
of the camera. Knowledge of this response can be useful for a wide variety of applications such as simulating
animal vision, colour correction and colour space transformations of the images captured by the camera. COTS
cameras are widely used due to their low cost and ease of implementation. We investigate a method of using a
Linear Variable Edge Filter (LVEF) and a low-cost spectrometer to characterise an RGB camera. This method
has the advantage over previous methods in the simplicity and small number of measurements needed for spectral
characterisation. Results are presented for three cameras: a consumer-level digital SLR and two point-and-shoot
consumer grade cameras, one of them being an underwater camera.