The methods of information theory are used in the discussion of observations under a microscope. Conclusions are similar to those obtained in a previous paper and exemplify again the difficulty of measuring extremely small distances. A comparison with the discussion of uncertainty relations shows that quantum uncertainties can be very much higher than the theoretical limit, especially when material screens or shutters are not being used and the observation is made on a free particle. This correction to uncertainty relations, however, does not introduce any change in the theory of quantized fields of Bohr and Rosenfeld.