Why sigma_data = 0.5 in EDM?

Hi, in Karras‘s paper Elucidating the Design Space of Diffusion-Based Generative Models, they specify sigma_{data} as 0.5, where is number come from?

That’s the standard deviation of the data. If you look at a more recent paper [2312.02696] Analyzing and Improving the Training Dynamics of Diffusion Models, that paper actually uses different data, so they could have used a different sigma_data; but instead they normalize the data to have standard deviation 0.5 so that they don’t have to change the other hyperparameters of EDM.