[font color=\'#000000\']This has been debated repeatedly, so I hope I do not open anothe can of worms by saying this, but ...
If you take photos the same angular field of view in different formats, and make prints of the same size without much cropping, you have to adjust the focal length in proportion to the format to kepp that same FOV, and to get the same DOF you must adjust the aperture ratio by this same factor.
For example, comparing 2/3" format to 35m film format, the size ratio is about four, and thus 10mm, f/2.8 in 2/3" format matches roughly 40mm f/11 in 35mm format: roughly normal field of view, lots of DOF.
The fastest aperture in current 2/3" format cameras is f/2, which matches f/8 in 35mm for DOF under these terms of comparison.[/font]