Ang25:  It is not just the physical size but the amount of weight in Mega bites  

An example okay:
you can have an original 1200 x 1200 @ 103mbs and you can tone it down to 1200 x 1200 @ 4mb...   and much lower...  BUT... The quality disappears as the weight gets lower...   so a balance is an essential...

Same image.. change size to 800 x 600 and it automatically can go down to about 20mbs from 103mbs.. but maintains exellent quality...(this is an example)

Size and weight...  balance..

  ----------------------------------------------------------------------------------------------------------------------------