View Full Version : Derogy petzval...with or with BIS

Jon Wilson
21-Dec-2011, 21:17
I have notice a couple of petzvals on this and other sites which describe Derogy No. 5 petzval lens, same FL, but one has BIS after its number. Is a there a practical difference between those lens or is one just a new "model"? Ford Fairlane vs Edsel? Eddie?

Thanks....BTW...how all have a Happy Holidays!


Steven Tribe
22-Dec-2011, 02:50
Bis is usually to denote a size (focal length) that has been introduced after the original manufacturers' model range was fixed. That is, a size 5 bis would be intermediate between sizes 5 and 6. There may be other design differences rather than FL in specific cases.

Jon Wilson
22-Dec-2011, 05:40
Thanks Steve. That is very interesting and helpful. Jon

Steven Tribe
22-Dec-2011, 06:26
The system is mostly used on German and French lenses.
Here is an example I have on a Berthiot trousse (casket) set.

Ramiro Elena
11-May-2012, 04:28
What would a 5-Bis be in FL? I can't seem to find anything on the VM.