I mean DOF compared with a 50 mm and 90mmm.
To me, to take pictures of people, the 75 mm offers a perspectve and a DOF very different of that of a 50 mm or a 90 mm. I find the results more charming and people friendly.
When you see the results of a portrait taken with a 50, a 75 and a 90 mm, for the same size of the visage on the print, the perspective and DOF of the 75 mm is the most charming. With a 50 mm you would have to come closer to your subject, wich would distort a bit more (nose looks more far from the ears, visage abit as an inflated balloon)) and it is the opposite with the 90 mm, whith which you would have a more flat picture (nose closer to the ears, as if you had a flat visage)...
Also with a 50 mm, you would need to be more intrusive and close to your subject, the opposite with the 90 mm, but due to the additional distance, you would be too far to obtain a close contact with your subject.
I hope this is clearer.
Best regards.