I checked that site against the instruction sheet charts that came with my 28 and my 105...web based computer is way off on DOF compared to Nikon literature...so it doesn't work with Nikkor primes...
I could be wrong but I'm pretty sure DX increases the DOF...
Marcel???
Here is my take on this. From what I was taught, DOF is dependent on a few things.
1-The distance from the lens to the IF (in focus) subject. The closer the subject is from the lens, the less DOF there will be
2- The focal length of the lens. The longer the focal length, the less DOF. This is where we say that you will have more DOF with DX since to have the equivalent view, the DX lens should be 1.5 times shorter.
3- The aperture. The smaller the aperture, the more DOF.
This is about all there is to it plus practice to understand how this translate into real photography.