Quote Originally Posted by Richard K. View Post
Sal, how much of a gap (at the top I assume) would there be then with a Fotoman holder? Significant enough to worry about light leaks?
Um, we'll also lose the top 1/16" of sky, er, I mean the bottom 1/16" of ground than we thought we had if the Fotoman is 1/8" less wide than the Lotus, no? :rolleyes:

-Richard
Here's what Paul Droluk posted about detailed dimensions of the Fotoman holders:

http://www.largeformatphotography.in...9&postcount=74

By comparison:
  • Outside width of Lotus holders is 2.0mm greater, so there would be that much more positional imprecision (along the rib) when a Fotoman holder is seated in a camera designed for Lotus.
  • Distance from taped end to start of lock rib is 1.4mm greater for Lotus. So, when a Fotoman holder is seated, its taped end would be 1.4mm further away from the back's stop, but locked in place by the rib.

  • Film channel width of a Lotus holder is 165.2mm. Fotoman lists a maximum film width of 165.7mm, so its channel is wider. Fotoman also lists a minimum film width of 162.7mm, which is exactly the low end of allowable widths provided me by Ilford's cutting room manager, which in turn was the lowest figure I obtained from any film manufacturer. This leads to the conclusion that Fotoman holders' "lips" will be wider than those on Lotus. Fotoman is probably trying to insure against users having problems with "oversize" film from lower-tier film suppliers. I don't know what difference this will make in actual exposed image area, which is 157.6mm wide with Lotus holders.


I've not seen a Fotoman holder yet. It is not possible to determine from these specifications exactly what differences will be evident between the two manufacturers' holders in terms of actual exposed image dimensions and location. I don't anticipate a discrepancy of more than a few mm, but at this point can't say with absolute certainty, since Fotoman's design decisions could move the "window" around within the outer envelope and still comply with its posted specifications. When a Fotoman holder is available, I'll test and report the results.

None of these differences ought have any light leak implications; they're so small that it's difficult to imagine a camera back which wouldn't seal despite them.