When I was in high school I worked for a photographer printing wedding pictures and helping out around his studio. The guy I worked for encouraged me to get a camera of my own and I bought a Nikon N70 with a Sigma 28-105mm f2.8-4 lens. I had a lot of fun with this set up but put it on the back burner when I went to college. After I graduated college I purchased a Nikon D90 body and I have been using the Sigma lens with my new digital SLR. I have been pretty happy with the results but I feel like I might be cheating my self. My question is: what kind of quality and mechanical issues am I going to face using an old (13 years old) film lens on my D90? Thank you in advance.