Right now, pressing left/right in Pholio causes the entire image to be reloaded from the server, even if the image was previously loaded. This makes it really hard to do comparisons between alternatives.
Potentially relevant: I see pholio preloading the images on pageload, but the server seems to be returning Cache-Control: no-cache, which might be what's causing Chrome to reload the image.
HTTP/1.1 200 OK Server: nginx/1.4.6 (Ubuntu) Date: Fri, 29 May 2015 19:17:18 GMT Content-Type: image/jpeg Content-Length: 598520 Connection: keep-alive X-Powered-By: PHP/5.5.9-1ubuntu4.9 X-Frame-Options: Deny Accept-Ranges: bytes Cache-Control: private, no-cache, no-store, must-revalidate Pragma: no-cache Expires: Sat, 01 Jan 2000 00:00:00 GMT X-Content-Type-Options: nosniff
It looks like it tries to preload (I see requests in the network tab in devtools for all the images in the mock as soon as I load the page), but doesn't do anything to keep the preloaded data around.