JPG
dimensions: 250x180
qulaity: 70%
file size: 23.7 kb

JPG
dimensions: 500x360
qulaity: 70%
file size: 65.8 kb

JPG
dimensions: 500x360
qulaity: 20%
file size: 20.0 kb

This example shows techniques found in the Lynda.com Online Training Library courses
Creating a Responsive Web Design (Chapter 12), and Working with PNG-8.