Best way to greater magnification for macro work

[Dr Klaus Schmitt]

I also heard that the RAYNOX is a cemeted 3-element design, which should explain why it is so praised!!

[bobfriedman]

some more raynox info from threads on photomacrography.com

http://www.photomacrography.net/forum/viewtopic.php?p=175487#175487

http://www.photomacrography.net/forum/viewtopic.php?p=126290#126290

http://www.photomacrography.net/forum/viewtopic.php?t=18145

[Akira]

I also heard that the RAYNOX is a cemeted 3-element design, which should explain why it is so praised!!

Klaus, according to the website of Raynox, both DCR-150 and -250 are of 2G3E design.  So, two elements are cemented.

Bob, the additional info is interesting.  Thanks!

[Akira]

According to Kenko, AC Closeup lenses No.2 (500mm) and No.3 (330mm) can be combined to make a No.5 of 2G4E design.  In order to calculate the exact combined focal length, you need to know the distances between the lenses screwed together, which is not given on their website.  I don't know whether their calculation is exact or rounded.

[bobfriedman]

using the thin lens formula it works out to be almost 200mm  1/f = 1/f1 + 1/f2

the only missing term is subtracted -d/f1*f2  where d = distance between them --   this term is very small