We already exclude Photon from being applied on admin, but not when working with AJAX in the admin.

Reported here:

• http://wordpress.org/support/topic/jetpack-photon-with-admin-ajaxphp?replies=1

Original trac ticket:

• https://plugins.trac.wordpress.org/ticket/1885