Hello Yanhong!



 Yanhong_Zhao:

Now I am wondering after applying random sized crop and random horizontal flip which essentially is generating more training examples in the data loader object so surely now my standard deviation and mean of the images will change a little bit.


It really doesn’t matter.  There is nothing magic about normalizing your
data to get exactly some mean and standard deviation – you just want
to get the general scale of your data to be sensible.
Unless there is something perniciously weird about your data, the
augmentation you are using will have very little effect on the statistics
of your data set.  You’ll be fine calculating the mean and standard
deviation of your original training set and using those values to
normalize your augmented set.
Good luck!
K. Frank