I've stumbled across a strange problem today and apologies in advance if this is an obvious one - i'm not a developer and am learning opencart as i go for our shop.
I ran a speed test of my site using http://www.webpagetest.org/ and pointed it directly to my store page - http://www.joaniesgifts.co.uk/store/
I noticed from the results that it was taking a long time to load the 3 Nuvo Slider images on the homepage which was weird because i'd optimised them. I noticed that the jpgs were 70kb each instead of the original loaded size of under 25kb. I also noticed the cache version was being used and the images were low quality.
I looked in my cache/data folder and sure enough the image sizes seem larger than my originals even though they seem lower quality than the originals...
Very confused whats going on - is it because i enabled cache in my htaccess file? How can i tell opencart to use my original files?
Any help/tips would be appreciated as i dont even know where to start with this one

Joan
ps. - my slider extension was this one here - http://www.opencart.com/index.php?route ... on_id=1475