EstimatingNoisePowerForAGivenSNR

xmipp_phantom_create_random -i phantom.vol -stats 1000 -ctf ctf.ctfparam -target_SNR 0.33333

The program generates 1000 random projection images, measures the average power of the signal before and after the CTF and computes the amount of noise before and after CTF that is needed to achieve on average the target SNR (Note that we talk of average SNR since each projection direction has its own signal power).

The program prints the histogram of the volume signal power (if run with a random description phantom file, this power histogram makes sense), the histogram of signal power and the histogram of the area occupied by the projection. The final output of the program is of the kind

For an SNR of 0.33333, a total noise with a standard deviation of 4.15773 is needed

You must use the number 4.15773 as the noise standard deviation in the Microscope program. /down3_11260_Periodogramavg.ctfparam you are an example of CTF file with CTF and background parameters.