Quote Originally Posted by Justin Cormack View Post
Fuji quotes it as 118x163mm (they sell half plate Acros, just got some).
That makes sense. Film sizes are always a few mm smaller each way than the glass plate sizes; this is done on purpose. It was originally done to accomodate the film adapter sheaths necessary to use sheet film in plate holders, and was never changed. That's why 13x18cm film measures quite exactly 5x7 inches (127x178mm), and 5x7" film is a few mm smaller...

The same strange "half-size" phenomenon is found in metric sizes too, BTW. 4.5x6cm is one quarter of 9x12cm which is one quarter of 18x24cm, and 6.5x9cm is one quarter of 13x18cm. But 9x12cm is not half a 13x18; and nothing whatsoever is half or quarter of 24x30cm. There was also a 10x15cm size which could possibly be said to be one eighth of 30x40cm, but neither of the two fit in with the other standard sizes in any logical way.