Have seen a few post referring to what I consider LF, as ULF and was wonder what is the consensus of where ULF begins? In my mind ULF would include the following common formats - 7x17 and 8x20 in the pano formats, 11x14, 14x17, 12x20, 16x20 and 20x24 as the most common UL Formats in use today. The formats of 5x12, 5x14, 7x11 are more like a pano version of 8x10, this based the fact that all are < 80 sq. in. = 8x10. The only more obscure formats of 8x12, 8x14 and 10x12 being somewhere in between LF and ULF.

Just curious what others consider ULF to be, or if there is a historic or more recent guide to describe ULF.

TIA