On Thu, Jul 22, 2010 at 2:09 PM, marco cammarata <marcocamma@gmail.com> wrote:
To convert the list into an array takes about 5 sec ...
Not too familiar with typical speeds, but at a guess, perhaps because it must convert 61.4 million (640*480*200) values?  Just to count that high with xrange takes 1.6 seconds for my computer.  I imagine doing further operations (like converting into a numpy array) on other Python objects (like lists) might be similarly slow. 

Ian