Solved by ptrblck in post #2 
              
              
                If I run your code, I get the valid error: 
RuntimeError: output with shape [1, 334, 690] doesn't match the broadcast shape [3, 334, 690]

which is thrown, since Grayscale returns a single-channel image, while Normalize uses three values. 
Fixing the mean and std to a single value, yields valid outp…