I have a few 8mm movie zoom lenses that fit this scenario. They can not be used on anything other than 8mm movie cameras, but it would be so nice to make them serve some photographic purpose again. Using them as a full lens is out of the question, so why not use part of them? The rear of the lens is too small to be useful, but the front element is large and can form images.
Two 8mm movie lenses. The one on the right is already removed from the lens barrel. Both are in similar focal length but the one on the right is more than a stop brigher.
To play with this lenses, you really will need a focusing helicoid, either buy one or make your own, or use a macro bellows. There won't be aperture settings, unless you plant them into an existing lens barrel that already have apertures. Using only the front element usually means the lenses are not optically corrected, as they would be when combined with the other elements in the original lens. This actually turns out to be even more fun than just using them as designed, because, they act like soft focus lenses! The un-coated lenses are even better than the coated ones for this purpose.
Front element of the Reflex Zoom f1.1 lens on the home made focusing helicoid.
The good news about making this kind of lenses is that they don't have to fit exactly. No worries about decentering elements, perfect focusing, etc. It's the effects that we are after. So, use whatever that you can to make it mount on your camera, even holding it with your hands!
I certainly had fun trying them out. It made me feel better that after many years of sitting around, digital cameras have made them into something useful and interesting.
Megan -- NEX-5 & the front element of an 8mm movie lens. Click to see larger.
My kids use to go nuts collecting and playing with this stuff, and I don't even remember what it's called. Now they are all in pieces collecting dust.
Soft lenses are best used with lots of bright colours and strong lights. Great for flower shots, but I don't have any to try. They are also good for some romantic Kodak moments of your girlfriend/wife.