Quote Originally Posted by Steve Smith View Post
Most lens elements you can buy singularly will be listed by their Dioptre* value. A Dioptre is 1 divided by the focal length in metres. So a 1000mm lens is 1D, a 500mm lens is 2D, 333mm is 3D, and so on.

150mm is 6.667D. To make it easier, 167mm (close enough) is about 6 Dioptres. To combine lenses, all you have to do is add their Dioptre values.

So you can create a 166mm lens using two 3D lenses or three 2D lenses or a 2D and 4D.

If I was doing this, I think I would do it with two 3 Dioptre lenses with the waterhouse stop exactly in the middle keeping it symmetrical.



Steve.

(* or Diopter for some reason if you're American)
Thank you so much for your help on this I think I kinda get it, I will have a look for that value when purchasing, I guess I could also make it from 6 1D lenses for example?