For me the readonly bit is a marker, that tells me 'this file should not be changed anymore...'
Peter
Hi Peter, all camera manufacturers chose the read-only bit as marker for tagging photos in-camera. Tagging the keepers so you don't accidentally delete them in-camera.
It is also the quickest way to do selects in-camera, for example when Bush arrived on his European tour last few months ago, his plane arrived about ten minutes before newspaper deadlines. You rattle off hundred photos hoping for a sharp one, quickly reviewing them on the camera when the action ends. I selected just two, with one push of the "lock" button for each. Then I told PM to ingest only locked (just these two), with few minutes till deadline, quick edit in photoshop and ftp'em back. This is the most common usage of the "lock" button, IMHO
So PM's behaviour is perfectly fine for me - I can ingest only the locked, when running out of time, and quickly rate them, edit them, ftp'em. If I had to ingest the whole take, switch to finder, untick EVERY photo as not read only, switch to photoshop, etc, that would be very slow.
I am actually glad it doesn't save the read-only bit.
Your mileage may vary, of course
But I just wanted to explain the most common usage of it.
Frantisek