Well, I am aware of the possibility to modify pre-ai-lenses. The original ai-modification-kits Nikon provided are no longer available. Altering the aperature ring mechanically degrades the lenses in my opinion, most of which are simply beautiful and very well done. Whether it is worth using old lenses on the D800 is an entirely different question. The answer Nikon gave with the Df is yes, that is the reason why the Df has this feature. What I am asking is, is it possible to refit the D800 with the Df AI tab ring. So far, no one seems to know.