Hi, it is. But the camera takes care of the aperture electronically. Leave at its highest F stop (smaller). Then select the desired aperture on the camera (front dial). All non G lenses work that way.

Hope it helps.

I use it mainly for portrait. But if the question is "how do you use the DC function?": Very easy.

You want to use it as a normal 135 f2: Leave it at is neutral setting.

You want to emphasize the background blur: Move the DC control towards the R. Start with matching the aperture set in camera and on the DC ring first see what it does for you. You can also have a "soft focus" effect by lets say having a F2 aperture in your camera setting and placing the DC ring at F2.8 (towards the R on the ring) or more.

You can do the same with the front blur. Just move the DC ring toward the F instead.

Shooting a lot will help you decide what settings you like. Just remember to refocus every time you play with the DC ring.

I hope it make sense to you (i am not the best writer out there).