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staft
01-01-2006, 01:43 PM
i have a zeiss-ikon folder with a nettar lens in a pronto shutter. i would like to try to remove the lens temporarily to try it with a pinhole. the outer and inner lens elements look easy, but the center element looks more complex to remove. has anybody tried this? can it be done without damaging the camera, and will the resulting shutter thickness allow for a full pinhole image on the 120 film?

ImageMaker
01-01-2006, 05:12 PM
The center element should just unscrew from the shutter, regular ordinary right hand thread (i.e. Righty Tighty, Lefty Loosey). However, it's probably very tightly in place. What I've done once or twice is, if there aren't little slots present, use a small needle file to file a pair of notches 180 degrees apart in the front edge of the barrel, then use a knife blade as a spanner to unscrew the element's cell. A ring wrench would be another excellent tool for this, especially if the outside isn't threaded; you can make one from hobby plywood if you've ever seen a picture, or if you want one that will last better make it from heavy hobby brass sheet (.032" thick should be fine).

For the front element, just remove the infinity stop screw and it will unscrew. The back one will probably require a little creativity, because it's also in there pretty tight (most likely) and though there are probably spanner slots already present in the cell, the convexity of the glass may prevent use of a straight blade spanner. Most I've seen could be removed by hand if you have strong fingers and the cell has a knurled edge (many do); otherwise, you might have to improvise a spanner (a length of .032" brass strip with a notch filed to clear the glass works pretty well for this).

If the shutter doesn't vignette with the lens (and it doesn't, I'm sure), it won't vignette with a pinhole in the same location. The only issue you might have is if you were to perform one of the "shutter in the bed" conversions to make a super-wide angle; a temporary conversion should be no big deal.

Do be aware, you'll have to reset the focus if/when you reinstall the glass; it's easy to do as long as the shutter has a B or T setting. Do watch that you don't reverse the middle element; not all lens setups allow this, but if you manage it, you'll get a very strongly curved field, focus shift as you stop down, and considerable spheric aberration once the lens is back in.

fhovie
01-01-2006, 06:20 PM
I bought two Icontas - both 6x9. One has a Tessar which is pretty good - the other had a Novar. Pretty bad. I unscrewed the front and rear elements with no trouble and I set a mounted Lennox Laser pinhole in on the iris where the front element had been. I used some thick sticky tape to hold it in place and it had performed flawlessly for me. A very simple modification.

staft
01-01-2006, 11:51 PM
the center element was held in place by a mostly-hidden spring clip- took a while to see, and i will have to sweep the floor tomorrow to retrieve the clip. otherwise, it is ready for the pinhole. thanks for the help, guys.