Figure 3: Asterix image: (a) the original grayscale image, quantized on 5 gray levels, (b) the read back from the sample (size m), rescaled to cover the entire black to white range and quantized on 5 gray levels to allow direct comparison with the original image, (c) the read back of the same image 7 months later. In each case the readout time is 20 ms/pixel at a power of 20 mW.