An Introduction to Responsive Images
Bruce Lawson @DrupalJam 2015 explaining how to Correctly-sized images for the device. This is a great and easily understandable talk to learn how to save bandwidth and speed up your site.
few quotes from Bruce presentation:
0.5 second delay = 20% drop in traffic (Google). 100ms delay = 1% decrease in sales (Amazon)
1 sec delay causes 7% drop in conversions (GlassesDirect)
5 sec improvement in page load time resulted in 5% – 12% increase in revenue (Shopzilla)
Ok? Now is the time to watch it