Wollensak Raptar 1/2" f/1.5 C-Mount Focus Is Off

[Matthew Hall]

I recently acquired this lens as my wide angle optics for a B&H Filmo 70-DR 16mm camera. A soon as I placed in into the turret and used the critical focuser I noticed a problem. Although the focusing ring turns easily and smoothly it is way off. When the lens indicates it is focused at infinity, it is actually focused about 3 feet in front of the camera. That is as far away from the camera as I can get it to focus. There is no visible damage to the lens so I am assuming that the three set screws on the focus ring itself have come loose at some point in the past and the ring got turned a bit before being re-tightened. Thus it now registers the focus distance incorrectly. Anybody out there have any experience with this lens as far as the internal structure? Is the stop block (which stops the focus ring from turning further than infinity) located on the focus ring itself or internally underneath?

I was wondering if I focused the lens to infinity, then loosened the three set screws on the focus ring and turned the ring to three feet, then re-tightened the set screws. Would that reset the focus distance? If the stop block is on the focus ring itself that might work. If it is deeper in the lens probably not. Any information would be helpful. Thanks

 

P.S.- I got a full refund from the seller so I am willing to experiment to try and get this working.

Edited November 21, 2024 by Matthew Hall

[Don H Marks]

Yes, the three tiny screws around the focus ring are the usual suspects for re-centering infinity. You can certainly do this yourself and get pretty close. 

If it is otherwise a nice lens, have just about any cine lens tech check it. This is a very common adjustment. In fact you should have all your lenses  checked. 

Edited November 21, 2024 by Don H Marks

[Matthew Hall]

I decided to take the lens apart to see what was going on. Turns out the rear grouping was extremely loose and needed to be tightened. But the real issue was with the front element. It is a rather deep element, extending down into a hole about 10mm deep. Apparently someone had been inside this lens (likely the same one who forgot to tighten the rear grouping) and upon inserting the front element got it jammed in there a little crooked. They decided to just screw in the front trim ring and call it a day I guess. The front glass was not completely seated and tilting at a bit of an angle. I was able to gingerly remove it and get it seated correctly. So now the lens focuses at infinity again and all is right with the world.

[Don H Marks]

Good work!

[Simon Wyss]

The Wollensak Cine-Raptar ½ in., f/1.5, from 1953 has eleven elements in seven groups. It had cost $99.68. https://alphaxbetax.com/wp-content/uploads/2024/08/1953-wollensak-masterpiece-cine-raptar-lens-selector.pdf

[Mark Dunn]

The Wollensak lenses were on the shelf when I worked at a weapons range. They'd been used on the high-speed Fastaxes before they were all Nikonised in, I assume, the 80s. But our 'standard' lens was a 500mm. mirror, so the 1/2" wouldn't have seen much use. We did have Zeiss 10mm. for the 16S, though. Got to use it once when I blagged a trial sponsor into letting me shoot a doco on 16mm.  instead of U-Matic.👍

Edited November 22, 2024 by Mark Dunn