why does itunes "optimize" my photos every time i sync Every time I sync my ipod touch, I sit there and watch "optimizing photos x of 1000" which takes forever. 

To be clear, I am not adding any more photos.  Shouldn't this only be a one time thing to optimize photos?
Why does it need to do this step every time?
I not sure why it does it every time, but the 'optimising' is basically shrinking their dimensions to the iPod screen size, thus saving space on the iPod.

I would therefore assume that it does it every time as it doesn't save the 'optimised' ones in order to save space on the computer.