Need 100mm lens cap

100mm filter ring diameter, or for a 100mm focal length lens? Push-on, screw-on, or snap-fit?

www.ebay.com/sch/i.html?_from=R40&_trksid=p2374313.m570.l1313.TR11.TRC1.A0.H0.X100.TRS0&_nkw=100mm&_sacat=79001

PF

Ah, now there is the right information.  I don't have any of the DE lenses, so I can't help as to what the cap size is, but I'm sure Biggles has the knowledge, what with his extensive collection of everything Yashica.

Basically though, you can figure out a filter size by measuring the outer diameter of a lens filter ring, then subtract two millimeters.  Say you are looking at a lens diameter of 54mm, you would normally need a filter size of 52mm.  That's because most filter mount rings are made of 1mm thickness material.  But not all.  There are the odd exceptions, but they are few and far between.  So a snap or screw-on cap in this example would also be 52mm, while a push-on cap would be 54mm.  And, there is the possibility that the filter ring on a Dental Eye is much smaller, fitting over the actual end of the lens optics, and not the end of the barrel.

From what I've seen of the front of a DE lens, you are looking for a push-on cap of plastic, with raised black letters (like for many of their other lenses), and you might just be able to do a search for "Yashica Dental Eye II lens cap" (no, that didn't work, no one had one separate from the camera that knew what it was).  I think all the II's and III's were of the same focal length, thus their construction could be the same.  The I is a shorter focal length (55mm), and has a fatter lens barrel.

Once you find out what the outer diameter of the lens front is, you can get any push-on cap the same size.  Some large format lenses take large diameter push-on caps.  It would look cool with a Schneider-Kreuznach or Rodenstock  cap.  Just know that many plastic push-on caps might not have enough gripping power anymore due to wear.

PF