Noise added by 8-bit compression using LOFAR test set A. Left image: result of calibration, 3C 196 subtraction and imaging without compression. Centre image: same, but before processing the visibilities were compressed using the 8-bit quantization scheme (4× compression) with the 2.5σ-truncated Gaussian distribution. Right image: difference between left and centre images – note the different colour scheme. Its rms is 430 μJy. The added noise is unstructured and well below the system noise, and the left and centre images are visually indistinguishable.