Also, Kodak used to offer a "Portra" filter, which looks to be plain glass with concentric rings cast into it. I have one in series VI. Never tried it. Don't know whether the center of the image is sharp and the rest soft. Might be worth looking for one if you're set up to use series filters already.

Well, I got the first results. I got some old lenses in shutters, probably removed from old folder cameras. In short, after some fooling around, I got "something" on film
One of the photos I like the most was shot with a 35mm lens - an old Russian Helios-44 (from a Zenit camera), on which I removed the back element.
Comments welcome - see here:
http://hrtranslations.com/photo/funky

Denis

Shot number 5 is interesting. It has kind of a 3-D look to it. Lens hacking is rather fun.