Thank you for posting link to my site! I can add that after NY I will post another article about 135 mm portrait monocle. The translation is almost ready. Everybody is welcome to ask me questions about the topic.
Very good! there are several loupes which can be used for that purposes. I tried some jewellers loupes and oculars from broken binoculars they do excellent wide angles. I just developed a 15mm wide angle conjugating a 25mm fl jewellers loupe with a front negative lens of a 0.8 cheap wider At f 11 it rivals the famous Hologon and has no vignetting nor variable density in the picture. if you have a precision lathe you can built your own. I shall give you all technical data. Regards LP Note: broken binocular objectives give excellent telephotos. The Kazan 8x30 binocular objective has exact 135mm. The Sergei Pozad 16x60 has a good 300mm.