p.1 #2 · Sigma 90mm DG DN Contemporary Discontinued. Replaced with the DG
AFAIK, DN denoted it was designed for mirrorless. I think Sigma is just dropping the DN part of the nomenclature as it is the de facto focus moving forward. I'm not sure I've seen anything where dropping the DN on an existing lens had a huge change to the product. But if that were the case, hopefully someone will jump in here.
p.1 #3 · Sigma 90mm DG DN Contemporary Discontinued. Replaced with the DG
They just decided to drop the DN since they are no longer releasing SLR designs. They rereleased the i-series lenses without the DN. The big change is the new 45mm F2.8 comes with a magnetic lens cap (the original did not). They are also using a different typeface.
