John,
HP is smoking dope. It is a physical limitation of the the printer.
When you feed paper, you need to "push" it underneath the print heads with a roller of sorts. At some point you run out of paper towards the end of the print so you cannot push it. That’s the back end margin. The only way around it is to fool the printer into thinking you have longer paper than you do, or it has to be inherently designed into the printer driver to do something like, or close to, borderless printing.
Photoshop reads your printer driver and those numbers in the grayed out boxes represent what your printer driver is telling photoshop.
Considering that, when you print a 4 x 6, if you tell your printer or photoshop to "Center" the image, the margins are taken into consideration. Since the back end margin is larger than the front end margin, centering is off.
The exact same thing happens in MS Word, only differently. In word, it will allow you to define margins that are beyond what your printer can print. You get a message that says something like "The margins are beyond the capabilities of your printer. Would you like Word to fix it or print anyway?" If you tell it to fix it, it resets the margin in the document, if you tell it to print anyway, some text may be cut off.
So again, it’s a printer deal-io.
Peace,
Tony
The PCL3 drivers on the HP printers I’ve worked with have something like NO margin at the top and a 1/2 inch margin at the bottom.
It’s even all around if you send to the the ps driver. You can attempt to offset this yourself if you move the page tool in AI, but I don’t think there’s anything similar to the page tool in PS.
