I'm not a Nikon guy, but I have two quick answers.
1) Vignetting is usually not a problem. Landscapes are usually shot with the aperture stopped down some, which makes vignetting all but disappear. And any that remains is easily correctable in post processing.
2) My DoF tool asks for the focal distance because it is used for the DoF calculation. It also reports the hyperfocal distance which is always the same regardless of focal distance. This is as it should be.
Thanks for your reply,
You are right i was looking at it the wrong way, indeed at F166 or F22 all vignetting should be gone unless the filter set-up is all wrong. That's one thing settled :-)
However what i meant in the DoF software is that it's asking for the "Subject" distance... When i use to do this manually pre-digital i never had to bother with the subject, for example i knew that on a 35mm lens set at F16 or F22 everything between let's say 10 feet and infinity would be sharp without ever knowing where the subject would end up (great for photojournalism), that is because lenses back then has the markings on the barrel, and even a $2K 24mm from Nikon doesn't have that.
I'll contact the makers of DoFMaster about that i guess.