EricWhiss, I'm genuinely interested in finding what is going on. You are making a claim which does not agree with theory, which is fine, as long as you provide the evidence (if you have experience publishing scientific papers you should be used to that, at least I am)
Nobody is forcing you to read this thread Synn, If you and many more are not interested just skip it, I don't have any issue.
Since I agree that this thread is not going anywhere if we don't provide any evidence, I made a test, which I will explain in detail.
If my methodology is wrong I'm the first one interested in rectifying it.
Test: comparison of DOF of images at same OUTPUT MAGNIFICATION using the following lenses:
1.- Hasselblad C 80mm Planar f2.8 (medium format)
2.- Nikon AIS 50mm f1.4
The camera used was a nikon D800. (the test is based on a different crops for each lens, so that OUTPUT MAGNIFICATION of the crop is the same, which would be equivalent to have the same angle of view in both formats).
Camera and subject was constant
Focusing distance was the closest possible with the Hasselblad 80mm (aprox 95 cm) without extension tubes
All files processed with default settings in LR, only the White balance was adjusted
Here are the results:
For the first test, the image to the left is the Hassy 80 @ f5.6, the center is the nikon @ f2.8 (2 stops compared to the 80mm) and the right one is the nikon @ f2 (3 stops compared to the 80mm)
The second test is the Hassy 80 @ f4.0, then the nikon @ f2 (2 stops compared to the 80mm) and finally at the right is the nikon @ f1.4 (3 stops compared to the 80mm)
My observation is that the difference between the two lenses which translates to same output size with equivalent fields of view is 2 stops.
I would really like (seriously) if you can share the results that show 3 f stops difference