Small amounts of analog noise (e.g., camera gain from dim lighting).
We computed the performance of the different weighting functions, using analytical formulas (Equations (24)–(26), for different camera gains α ∈ 0. 25, 0. 5, 1, 2, 4 and different offset noise levels σ o ∈ {0.001,0.5,1,2,4,8,16}.
Also, using the phase information of the Gabor filter rather than amplitude is known to result in robustness to different variations such as illumination variations, imaging contrast, and camera gain [7].
Given corresponding pixels x t and x t+1 in the frame pair, pixel intensities are related by the multiplicative camera gain model: f^{t+1}left(mathbf{x}^{t+1}right) = beta {f}^{t}left(mathbf{x}^{t}right) (2).
In TGL mode, the delay time between excitation pulses (for 10 μs) trigger off and camera gain trigger on (for 10 μs) was varied in the interval between 0.6 and 275 μs at cycle frequency of 3 kHz.
Furthermore, in the process of Gabor transformation, DC-free Gabor kernel is adopted because of its invariance property to the ambient illumination [32], while Gabor phase features of irises are assigned regardless of how low the image contrast, illumination, and camera gain [33].
Results are again generated for different camera gains α ∈ 0. 25, 0. 5, 1, 2, 4 and different offset noise levels σ o ∈ {0.001,0.5,1,2,4,8,16}, for a CRF modeling gamma correction γ z) = z0.4 under (1) the assumption that the CRF is known in advance, and (2) by estimating the CRF from the images.
We imaged these spheres with exactly the same instrumentation parameters (camera gain and temperature, exposure time, magnification, etc).
Wild type and α9−/− tissue sections were processed simultaneously and resultant labeling was examined by confocal microscopy, ensuring that the laser intensity and camera gain were held constant.
