17675 ring for Leitz enlerger lense

[fred_obturateur]

I have noticed Leitz Focotar-2s are sold with a ring that is roughly

20mm-long. What is its purpose? Is it an "adaptor" for other brands of

enlargers (other than Focomats Ic?)

Thanks

[ronald_moravec1]

I am suprised nobody has voluntered on this one. An small extension tube is required to space the lens the correct distance from the negative on focomat 1C enlargers. The bellows and focus helicoid are short and the extension tube is used to make up the distance.

 

The focotars had other uses within the Leica system and this allowed a universal system lens. You also have the ability to use the focotar on other enlargers whose bellows may not have compressed enough to accomodate a longer mount

[edward_zimmermann]

"<cite> The focotars had other uses within the Leica system and this allowed a universal system lens. You also have the ability to use the focotar on other enlargers whose bellows may not have compressed enough to accomodate a longer mount</cite>"

<P>

This is, of course, backwards...

<P>

The Leitz Focomat/Valloy enlargers were not always provided with objectives and so were designed to be used with the taking lens of the camera (for example the 1:3,5/50mm Elmar). This means that the mounting threads to film plane distance is less than in enlargers not designed for this--- lets one, btw., also use a 35mm "out of the box" for smaller formats (film guides were made for quite a few film formats from 8x11mm up to 4x4cm). The flange focal length of a typical 50mm enlarging lens is around 43-47mm. The flange to film of a LSM ("<cite>Leica Screw Mount</cite>") is 27.8mm. This means that one needs a 16-20mm or so extension tube to get the enlarging lens to the right flange to film distance. Leitz early on made some special enlarging lenses like the Varob and enlarging Elmars and these were enlarging objektives set in a non-removeable extension tube--- I have one of these from 1940 that came with a special version of the Focomat called the "<TT>VUTOO</TT>" that has a large baseboard (63x65cm) and a tall (120 cm) and very thick column (5 cm) which I suspect was intended for military and espionage applications (recall Leica's role). Latter Leitz adopted the Focotar (which was OEMed from Schneider) and provided a seperate extension tube. This tubes are NOT specific to the Focotar-2 but are needed by any 50mm objective, save those that already incorporate one into their design, on these models of Leitz enlargers to correctly focus.