Help me to recognize this mysterious lens...

[massimo.stirner]

Hi,

I'm going to buy a large format wooden camera, exactly 18x24, but I don't recognize its brass lens. I only know it's a Rodenstock Bistigmat. I have found out some data in this web article:

www.museum-digital.de/san/singleimage.php?imagenr=6662&am...

If you click on pdf you can read further information provided you use google translate. But I couldn't deduce its focal length or highest aperture. The seller doesn't own additional lens shown in web article above.

I neither try or see it. The seller have only sent me these pictures:

http://www.flickr.com/photos/73235476@N04/7937299526

I wonder if anyone of you can help me?

Thanks. Massimo.

[Geoffrey_5995]

It looks like an early Bistigmat Rodenstock convertible set. I've never seen the convertible version of this lens but the Bistigmat was a lens designed to correct for visual and chemical focus. These come up for sale from time to time on eBay. I believe the Bistigmat was a Periscop design meaning that it was a doublet with two pieces of glass, one in front and one in back which would mean that it was not corrected for chromatism. The mechanical design of teh Bistigmat took into account the chromatism so after focusing visually, the lens would be adjusted so that the correct distance to the film plane would be achieved for the sharpest possible result with this type of lens. Hope this helps.

[Ole Tjugen]

It's what it says on the box lid - "Rodenstock Bistigmat Objektivsatz"
Meaning that it's a casket set of Bistigmat lenses. Looks like there are 7 single lenses of different focal lengths.

[Steven Tribe]

I can see one of the lenses is engraved 55 (cm) - so it is likely this casket set was designed for 18x24cm plate cameras. When you have this many combinations, some coverages will be less than, in this case, 18x24cm - whilst single lens use would cover much more.

Rodenstock would just not let this antique system die! In 1911 they still had the standard "bistigmat" range and a newer casket set called "Ortokromatisk Bistigmat Objektivsats". This had 4 identical focal length lenses - 2 in plain glass and 2 in yellow glass. So you had to remember the right combination of lens colours, which colour should be nearest the plate, the "filter" factor (1 or 2 yellow lenses), and change the lever after focussing.

[Ole Tjugen]

A "standard casket set" contained 7 cells: 15, 25, 35, 45, 55, 65, and 75 cm focal lengths.

While the shortest combinations wouldn't cover 18x24cm, it was common to use format reducing inserts to fit smaller plates in large holders. My own 24x30cm camera came with a complete set of reducers to 18x24, 13x18, 10x15, 9x12 and 6,5x9cm. That makes the 106mm shortest combination a "normal lens" for 6,5x9cm, and the longest (750mm) a long lens even for the full format!

Somewhere I have a focal length and effective aperture table for these sets - you can barely read it on one of the photos here: www.casket-set.com (http://www.casket-set.com).