Kern Yvar 75mm f/2.5

[Andrew Hamilton Watts]

Hi all, 

I recently acquired a Kern Yvar 75mm f/2.5 and have a few questions on the lens. I cannot seem to find much information on the f/2.5 other than it was made sometime in the late 1940s before switching to the 2.8 model. Does anyone have experience in the 2.5 version? How does it compare to the others? (note: that is not a big concern of mine, I am just curious about it). 

Second, the front element is pretty dirty and I am wondering if there are cleaning solutions I should avoid or that others would recommend for cleaning the lens. I know some lens cleaners can take the coating off a lens and since this is so old I am a bit hesitant to start that. 

Any other information of thoughts would be appreciated. 

 

Best, 

Andrew 

[Simon Wyss]

It’s a 1943 triplet but of a design different from the f/2.8. You probably have a non-coated one, Kern had begun to bloom glass elements in 1944 and that only partially at first. The 2.8 came in 1949.

To clean do remove all hard debris with compressed air or a rubber bulb. With a clean microfibre cloth take off loose particles lightly, apply air one more time, then turn cloth over, wipe with the finger in cloth a bit harder, always in circles from center towards rim. To finish off, wipe over with a soft hair brush such as those that women buy in the make-up department.

To use liquids I do not recommend because you might affect the matt paint in front of the first element, smear it on the glass. That would be annoying.

[Andrew Hamilton Watts]

36 minutes ago, Simon Wyss said:

It’s a 1943 triplet but of a design different from the f/2.8. You probably have a non-coated one, Kern had begun to bloom glass elements in 1944 and that only partially at first. The 2.8 came in 1949.

To clean do remove all hard debris with compressed air or a rubber bulb. With a clean microfibre cloth take off loose particles lightly, apply air one more time, then turn cloth over, wipe with the finger in cloth a bit harder, always in circles from center towards rim. To finish off, wipe over with a soft hair brush such as those that women buy in the make-up department.

To use liquids I do not recommend because you might affect the matt paint in front of the first element, smear it on the glass. That would be annoying.

Awesome! I appreciate the information. The lens is marked with AR, which I would assume would be a coating on the front, but I have limited knowledge of lens coatings. Either way, I will avoid liquids and follow your advice. 

A follow up question, can you (or anyone) recommend a lens cap for this, or what size I should be looking at? It came with a much more contemporary plastic one but it doesn't really fit. 

 

Thanks, 

Andrew 

[Simon Wyss]

Yes, AR is the abbreviation of Anti-Reflex (treated).

About the frontal thread I’m not sure. M 40 × 0,5 it could be. Kern had made aluminium screw-on caps with their name embossed but anything with the fitting thread will do.