Originally posted by Adam Plus, with a fisheye, don't you just leave it at infinity most of the time and let the DOF do the work?
Nope! As an owner of the Zenitar 16/2.8, I can attest that accurate focus is as critical with this lens as with any other, just more difficult to attain. The focus throw is fairly short and it is difficult to tell when you are in focus for moderately close subjects. (Everything is sooo tiny in the viewfiender!) Remember that for a given subject size on the focal plane, the working distance is much less with the Zen than with a longer lens. As a result, DOF is not really that much better. I have plenty of out-of-focus shots that demonstrate the principle quite nicely.
To the OP, I can suggest that an aftermarket focus screen with split image and/or microprism may be a good solution. I know that it makes all the difference for me. Your post indicates that you get poor results beyond 8-10 feet. Do you mean closer or beyond? If beyond, you may want to double check that infinity focus on your Zen is properly set up. My lens, when I received it from Russia, could not focus past about 10 feet. This is an extremely common issue. Correction involved adjusting the infinity stop for the focus ring. The adjustment is easy to do, but is best done using a body equipped with a horizontal split image focus screen and a distant vertical object.
Steve