Funny you should say that, as we speak a Heligon f/1.5 is on my desk in pieces. Because the f/1.5 version of this lens has even shorter working distance than the f/1.6 version, I never used it. I decided to see if I could rearrange the lens elements to see about getting infinity focus. I pulled all of them out and started putting them back in with different combinations until something made focus. Right now it looks like I have three elements on the desk and 3 in the lens. Not sure how useful it will be as I haven't used it much yet, but I got it to focus to infinity.
Interesting observation and experiment, Charlie. Thanks for the heads-up. I'd like to echo the warning regarding the 100/1.5 Heligon: it is way inferior to the f/1.6 in terms of practical usability due to the very short back focus distance (that is, unless you pull the lens apart into separate components
). Thus, stick to the 100/1.6.
I expect most of the optical power resides in the (heavy) front group(s) and that the rear group(s) are added to correct aberrations downstream. Seen as a whole our tests on "massacred" lenses confirm this.
A slide projector lens probably will perform equally well (sic) and might be worth looking into. Heligons have seen a substantial price hike due to the rekindled interest in them, so always beneficial to have a cheap alternative for experimentation.
