Close
Photoshop, 5000x5000: 60 seconds (!), 9921949 bytes.

pnmtopng (rudimentary Unix commandline tool--does nothing fancy, just passes to libpng): 10 seconds, 10558834 bytes.

60 second saves are useless; multiply it by a set and it can easily waste over an hour just compressing. For an under 10% difference in size, it's a joke. (Especially since while you're saving in Photoshop it can't do anything else, and it refuses to open a second instance ... even though I'm on a quad-core, 8gb system. Adobe *cough* rocks.)

These weren't run on the same system--pnmtopng on a Q6600, Photoshop on a Q9300, which is similar and slightly faster.