I have a question concerning the SIGMA lenses:

What are the differences (if any) between the SIGMA lenses for NIKON cameras with the label "D" (e.g. 28-135mmD) and the same lenses without a "D" e.g. 28-135mm) after the focal length indication? (It is printed only on the side of the objectives, but not in the catalogue) Are there technical improvements in this new "series" (with a "D") with respect to the previous ones (without a "D")?

A dealer told me, that all SIGMA lenses for Nikon AF are "D" compatible lenses (they can provide distance information to the camera) (with exception of the 24mm f2.8), not matter whether they have a "D" explicitly written on the surface or not. SIGMA has recently changed the "name" to stress the fact that they are "D"-compatible (in analogy to the AF-D Nikkor lens), but they have been already "D" compatible since many years.

I have noticed, that since a couple of months the lenses "without a D" have been replaced by the ones "with a printed D" in the shops. However, I haven't seen any reports or notes about this anywhere.

Does anybody knows the answer? Thank you very much!

-- Cesar Fernandez (cesar@mol.biol.ethz.ch), January 22, 2001