To tell the difference between a Heliar type and a Tessar type, count reflections.
The Tessar front cell consists of two singlets, so has four air-glass interfaces and no glass-cement-glass interfaces. Four strong reflections, no weak reflections. The Tessar rear cell is a cemented doublet, so has two air-glass interfaces and one glass-cement-glass interface. Two strong reflections, one weak, which may be hard to discern.
The Heliar is a little more complex. One cell consists of a cemented doublet and a singlet, four strong reflections and one weak. The other cell is a cemented doublet. Which combination is in front varies with the lens model and maker. Voigtlaender seems to have put the doublet in front of the diaphragm, the doublet and singlet behind.
Arne Croell (see
www.arnecroell.com/voigtlaender.pdf) reports "The Universal-Heliar (table 4) was a real soft focus lens, where the biconcave center element was moveable with a ring at the front of the lens to adjust the soft focus effect (fig. 5)." OP, if your lens
is a Heliar type, does the biconcave singlet move?
Yamasaki made a 360/4.5 Tessar type. OP, it's hard to be sure, but I suspect that's what you have. Please count reflections etc. and report back.
Bookmarks