Restrict size of file uploaded with file_column


I am using file_column to create and store thumbnails of users images.

file_column :image, :magick => {:crop => “1:1”, :size => “70x70” }

I have tried to restrict file size by using

validates_filesize_of :image, :in => 50.kilobytes…200.kilobytes

But this works only in the sense that it will compare the size of the
file after the crop.

How can I check that the size of the loaded file is valid?