>The Sigma (1,5 or 1,6 diopter) can also be found in 52mm and 62mm(and "replace" Nikon 3T and 4T). The 58mm was offered as a specific
CU for their 70-300mm lens.
Fascinating. The famous "Achromatic Close-Up Lens Page" (http://www.angelfire.com/ca/erker/closeups.html) mentions only the 58mm version. And that was the only one I ever found on the B&H web page (when it was available).
I have found a 52mm and a 62mm in used filter sections of canmera stores. On the ring it says Sigma Achromatic. Sellers knew what they were as their price was B+W like.
>The Nikon 3T is a 52mm and the 5T is a 62mm, both are 1,5 diopter.Same pattern for 4T and 6T (2,9 diopter). I was thinking about somebody using it on a typical Pentax normal lens with 49mm filter size, but 62mm might in fact be more versatile as it would fit "bigger" lenses like the 135/2.5 for example.
Both the 3T and 5T are supposedly for longer lenses (80mm-200mm) Mark Roberts
They are indeed too weak for a normal lens, 4T and 6T would be better.
Andre
