Image / Photos, What size should be loaded to Prestashop? Site is slow.

[sipus]

My site is very slow to load.

 

Firstly because I had way too many attributes and combinations. however now i have the attributes and combinations wizard to solve this.

 

I am concerned that it is the size of the images i am uploading that are causing the site to be slow.

 

I would like to know what size the images should be to load to the site or if anyone has any suggestions why my site is running slow??

 

TIA