Dear Matt,

1.6-1.8mm including gelatine on half a dozen I just measured.

Register should not be a problem as most plate-holders push the plates forwards against the front of the holder, i.e. any variation is behind the plane of focus.

My Gandolfi plate holders will take anything reasonable, probably up to 2.5mm, maybe even 3mm, while my Linhof film/plate holders (all sizes) look to be good for just over 2mm.

Cheers,

Roger (www.rogerandfrances.com)