1. Test shots with both versions of Mamiya ZD back

Strange effect of purple spots - depending on increasing exposure times - in dark areas on pictures shot with ZD back and ZD back DB.

Mamiya ZD back DB (left), ZD back (right)
Mamiya RB67 Pro SD with ZD Back DB
Sekor C 4.5/50mm
ISO 100, t=7", F/11, YB401 
 
Detail
 
Mamiya RB67 Pro SD with ZD Back DB
Sekor K/L 3.5/127mm
ISO 100, t=5", F/11, YB401 
 
Detail
 
Mamiya RB67 Pro SD with Standard ZD Back
Sekor C 4.5/50mm
ISO 100, t=7", F/11, YB401 
 
Detail
 
Mamiya RB67 Pro SD with Standard ZD Back
Sekor K/L 3.5/127mm
ISO 100, t=7", F/11, YB401 
 
Detail
 
Picture noise at exposure times longer than 4 sec.
 
Detail