After reverse engineering the limits and then later being pointed
to the documentation about the limits, a birdie dropped a hint
into my inbox telling me to try using a progressive JPEG file.
Within just a few minutes, several people also chimed in noticing
that the large iPad hero image is a progressive JPEG. I’ve not
used progressive JPEGs in years, but following the lead of the
birdie and the crowd, I gave it a shot. Lo and behold, it’s
indeed the ticket to large JPEG joy on the iPad Retina display.