Don H Marks

Good as new!

Re-assembled to the correct orientation for the H8 with new grease. 

The focus ring was cleaned and re-greased. Not it is nice and smooth. 

The focus ring was still stuck. 

Under the thick grease is a locking screw that needs to be removed to get to the focus ring. 

The focus mechanism came apart with exactly two turns. It was not that bad, but it was cleaned and re-greased.

This one appeared to be simple threads with a single start location, not really a helicoid. 

The grease had turned into something resembling wax. 

Mark the focus mechanism before sliding the lens apart. 

Three screws around the perimeter can be removed to access the frozen focus mechanism. If I plan on re-assembling in the exact same way, I remove the screws all the way, so the indentations can be seen to aid re-assemble. 

In this case, I will rotate the lens when I re-assemble it, so the index marks are in the correct place for the H8. 

I picked up this mint condition Yvar 75mm lens for my H8 Bolex. The optics are perfect, but the focus ring is frozen. 

I found a 75mm Yvar and it works great on my H8 non-REX with the adapter I got off e-bay.  For those that don't use 8mm, the lens is useable on that camera because the H8 Octameter has a 75mm setting. 

After servicing the helicoid, it was easy to re-assemble the lens so the index marks were in the correct positon with the adapter in place. For this camera I want the index marks of all the lenses on the left side. 

That is very nice, thank you for the link. 

I built mine to try time-laps to see if I like it before buying gear I might not use much.  

A short video of the intervalometer in action:

The servo cycles back and forth and pushes the frame release forward via a spring-loaded lever. 

I put together a simple intervalometer for one of my Bolex cameras. 

The design uses a Radio Control Vehicle servo and a simple 'servo tester' box that cycles the servo at various speeds. 

I did contact Rafacamera about adapters for these lenses. Based on that outer measurement of the threads he indicated the m28x0.5 to m52x0.75 adapter already in stock might fit. Also, may be able to custom make other sizes. 

Maybe I'm not looking in the right place, but I find it hard to believe there is no big list of D-mount lenses compiled to a table or single website. 

I have collected some pdf files listing D-mount lenses but only for Kern, Berthiot and Wollensak. Even then, I think I have only partial lists. 

I do get 27.9mm when I measure the lens cap threads on the D-mount 36mm 1.8 Switar. Same size as the 13mmm 0.9. 

Without actually dismantling the Yvar 13mm 1.9, I'm a little suspicious if it is really six element, because in another catalog "February 1952" the same diagram is used for the Pizar and or Switar 12.5mm:

Thank you for the correction on the Switar 36mm 1.8 as being 5-element. 

I also found a Bolex catalog in my collection of physical documents. Its content is a little different from the PDF files I have collected. 

In that physical catalog (November 1952) it is showing the 12mm Yvar 1.9 as six-element. If so, that is the only six-element Yvar I have come across in my stash of Bolex literature. Most Yvars being 3 element with a few exceptions. 

After years of searching I finally found a second 27mm lens cap. As far as I know only the Switar 36/1.8 and 13/0.9 used that lenscap and I only had one to share between the two of them. I don't think any of the other D or C mount cameras used that size. 

The way I found it was just scanning many images looking for the distinctive relationship between the Kern/paillard text and the size of the cap. It is uniqe none of the other caps look that way. 

The little Switar 5.5/1.8, however,  takes the easy-to-find lenscap common to the Yvar D-mount lenses. 

That post makes me feel like one of the youngsters. Those cameras were all from before I was born. Though, only by one year. 

Another good rule of thumb is that one can't make a focused image if the subject and film are less than 4 focal lengths apart. 

This is not my picture, I found it on the internet. But it does show what I have in mind. You can see the adapter on this one is a vintage piece. Though I can't make the letters other than U.S.A

Mine just came today. 

I don't have a standard C-Mount lens to test yet, but I did measure it and it will likely work. I got these numbers off the internet, not sure how correct they are. 

D-mount flange focal = 12.29
C-mount flange focal = 17.526mm
Difference = 5.236mm 

I measured the adapter and it was about 5.18mm +/- some hundreths. 

The lens I have in mind is the 75mm Yvar, as my Octameter has a setting for 75mm. 

Another I was looking at was the 3"  Wollensak.