mennoblaauw

I have a 1600F with the 60mm/5.6 as well as the 60/5.6 for the 500C. I tested both using the CFV-ii back, and I can't tell the results apart in any way. I think they're magnificent, even wide open. I also tested the 60mm/3.5. It's in the same quality ballpark, but of course the 1.5 stops extra make life a lot easier when using it. What I found most remarkable with the 60/5.6 was the complete absence of ghost reflections in evening photography. (Photo taken at f5.6, 1/100, 3200 ASA, CFV-ii back mounted on 1600F body).

The 250mm Sonnar I recemented a year ago is just fine, resolution tests prove I got that one right. Phew.

It;s been a while but I learned some things in the meantime. I recemented a Kodak Ektar for a 1600F, and I am now working on a 6-element Planar that had separating front elements. I also ruined such a Planar, by sticking the front elements in the oven and opening it before they had cooled off, leading to cracked glass. So for the new attempt, I wanted to be much more careful. I looked at the materials used nowadays to cement optical elements, the UV-cured plastics, and found that dichlorinemethyl (CCl2H2) might dissolve it. To test that, I separated the rear elements of the ruined Planar the old way: In the over at 180 Celsius, the plastic melts and the elements come apart quite easiy when gripped with rubber. Next, I tried cleaning the exposed surface of cement remnants with MEK, acetone and CCl2H2. Nothing seemed to cut the plastic. But after two weeks submerged in the CCl2H2, I can see the remnants disappearing. Now that is a lof of surface area accessible to the solvent, so I expect that soaking the front elements until they come apart will take time - like months. I'm three weeks into that now, and I can see the separation getting worse, so something is happening!

Thank you for the good advice, Ed! I'll try the solvents you mention next time. Not scratching the glass with a knife is not ony a matter of hardness of the materials, but also of the angle, the sharpness and smoothness of the edge of the knife and careful handling. We can shave without cutting ourselves, right? Also, fixating an optical element in a horizontal plane only requires three points. That's what three water glasses can deliver just as well as any precision tool. Positioning the water glasses themselves, relative to the narrower optical element was the tricky bit. I'm certain I achieved about 0,1 mm precision. I'll measure it and let you know when the balsam has hopefully dried, in a week or so. As an experimental physicist raised by experimental researchers, I was taught to try and overcome any limitations I might run into. best regards, Menno

I just did this with separating elements 3 and 4 of a 1957 Sonnar 250mm. After taking the glass elements out of the metal parts, it turned out I had to heat them to 180 Celsius before the polymer cement would soften enough for me to twist the elements apart. Next, I scraped off the remaining cement with a sharp knife, since nothing would dissolve it (I tried acetone, white spirit and ethanol). The glass is hard enough to allow for this without scratching. Then, I applied two drops of Canada balsam (dissolved in Xylol, available for microscopic purposes) to the center of the larger element, put the smaller, wider element on top and saw the balsam distribute evenly by itself. The smaller element is wider that the larger one, so I had to align by unconventional means while drying. I used three water glasses to hold the smaller element precisely aligned with the larger, narrower one. Easy to do by eye because any misalignment showed up as a crack in the black paint on the outside of the elements. All in all a few hours work, and weeks of waiting patiently for the balsam to dry and harden. I kick-started that process with a few hours in the oven at 100 Celsius. Canada Balsam spills dissolve easily in white spirit, and the stuff melts at 50 Celsius or so, so there is no need to fear having to try again.

Thanks for that, Orsetto! I find the waste-level viewfinder of my Hasselblad 500C has the same -1 optics as the Nikons of the same era, but the HC-1 does not - that's why I needed the Nikon eyepiece "-2" (so that is -1 in real diopters) correction lens installed in it. And indeed, it is the 20mm knurled ring size of the Nikon part that fits the slot in the rubber eyecup of the HC-1 precisely.

And another 7 months later: I just managed to stick a later-version Nkon eyepiece correction lens (of the FM3a/FM2/FA/FE type) into the rubber eyecup of the HC-1. There s a groove there, apparently inteded for this purpose, that happens to fit the outer rim of the Nikon eyepiece. When I put it in with the thread poining outwards, I was able to fit the combination back on the HC-1 all the way, very snugly. No glue needed, just some patience. The Nikon eyepiece -2 on the HC-1 gives me the same characteristic as the standard Nikon viewfinders from the Nikon F era - that is, where I normally need -1 glasses because I'm a little near-sighted, I see the ground glass perfectly focused with my glasses off, now that I'm older and need reading glasses to focus at 1 m distance, where Nikon used to position the image of the ground glass. Younger people don't even notice this... Anyway, the short version is that the later, smaller Nikon eyepiece correction glasses fit the HC-1 rubber eyecup tightly and perfectly!