15cm Tessar Front Element Disassembly

[rjbuzzclick]

Hi,

I have a Carl Zeiss Jena 15cm f/4.5 Tessar lens on my Pre-Anniversary Speed Graphic that has some haze between the front elements I'd like to clean up. Since the front elements should not be a cemented pair, I just need to get them out of the barrel to clean them. I have done this before on other lenses, but not on this specific one. With the front group removed from the shutter, it looks like the back element may unscrew, as there is some knurling around it, but it also might be pressed in (see second picture). Has anyone assembled one of these and know which it is? The back element would be easier to get a grip on to remove if it unscrews rather than using something like a rubber stopper on the front name ring. There are no holes for a spanner in the front ring.

Thanks in advance,

Reid

 

[Dan Fromm]

I don't have a 15 cm 1:4.5 Tessar, but have a 15 cm 1:6.3 of roughly the same vintage in front of me. I just screwed the front cell out of the barrel. The front cell's rear element unscrews easily, grab the beaded edge and turn counter-clockwise.

 

[Donald Qualls]

Confirmed. My 15 cm f/4.5 Tessar (older than yours, 5 digit serial) in the same model dial-set Compur, works the same as Dan's f/6.3 version. Second element just unscrews from the front group cell with fingers.

 

[rjbuzzclick]

That's great, thank you both very much!

 

[rjbuzzclick]

"The front cell's rear element unscrews easily..."
"Second element just unscrews from the front group cell with fingers."

Ha! Mine proved to be a bit more stubborn. It took two rubber gloves, a jar opener mat cut in two, two days of alternating treatments of mild heat and Liquid Wrench (sparingly applied to the joint), and finally a few light taps around the perimeter of the front cell with a rubber mallet.

Regardless, having confirmation I was disassembling correctly was a big help! Thanks again to you both!

Reid

 

[Donald Qualls]

Yeah, it's good to know it does unscrew and in the normal direction before you start applying additional torque or other assistive methods...

 

[Man-Wei]

Thanks, good to know how the front lens group disassembles. Now I wonder if it is fair for me to assume that the Carl Zeiss Jena 12cm f4,5 front lens group disassembles the same way. I have one that need a bit of cleaning.

 

[Donald Qualls]

Tessar type and Cooke triplet lenses have the same arrangement ahead of the diaphragm(/shutter); they differ in having a simple glass rear element in the triplet, or a cemented doublet in the Tessar type. A 5-element Heliar has, IIRC, even a third cemented element in the rear group -- but the same setup for the two front elements.

 

[Man-Wei]

Tessar type and Cooke triplet lenses have the same arrangement ahead of the diaphragm(/shutter); they differ in having a simple glass rear element in the triplet, or a cemented doublet in the Tessar type. A 5-element Heliar has, IIRC, even a third cemented element in the rear group -- but the same setup for the two front elements.

I left out that I am referring to a Carl Zeiss Jena 12cm f4,5 "Tessar" lens.
I read a lot about Heliar lens. May be one day I will acquire one. Thanks.

 

[Donald Qualls]

I am referring to a Carl Zeiss Jena 12cm f4,5 "Tessar" lens

The only difference among actual Tessar lenses (including Tessar types like Skopar) is whether they're set up for front-element focusing or unit focusing. Nearly everything in the 120+ mm focal lengths is unit focusing, and the only difference with the front-element focusing type is the infinity stop and four-start focusing thread (= 3 ways to get the lens back on so the focus scale doesn't match the actual focus).