Please bear with me ...

I'm trying to create a workflow that will create a balance between image size and quality. My idea was to convert my edited original images into PNG files (sized for the Large Images parameters – the default 2048x1536) and let Juicebox create the different size jpegs when they are uploaded. That way, none of the images are are being subjected to jpeg compression more than once.

Seemed to work great for the small and medium sizes, however the large jpegs are HUGE – anywhere from 2.3 to 4.7 MBs, even when the quality setting for the large images is set as low as 55%.

When I take the largest PNG file and process it in Photoshop with 55% quality setting, I get a file that's around 550K – that's a huge difference.

Can you help me understand what's going on here?

And what are your recommendations for image sizing and processing to maintain the best balance between quality and performance?