Shape and level of the noise floor depends on the pixel size and SNR.

(A) Illustration of the inverse scaling behavior of the spectrum with pixel size. 1 × px corresponds to the experimental pixel size. The shape of the noise floor is the result of the pixel-noise being convoluted with kernel from the linear interpolation. (B) Plot of the spectra obtained for different SNRs. The noise floor decreases for higher (better) SNRs. At high SNRs (SNR ≥ 104) it begins to enter the noise due to numeric imprecision. Since this noise is independent of pixels, spectrum for SNR = ∞ is flat (red line).