Actually, that's not really depth of field in the conventional sense, it is achieved by tilting the lens forward to get the plane of focus to leave from under the camera and project out to the distance. This gives a "cale de netteté" that gets taller as it goes away from the camera. It's known as the Scheimpflug principle http://www.trenholm.org/hmmerk/#SR. I just looked up the Wikipedia page in French ; it's really poor and not easy to understand. Merklinger's books are well worth the read since you seem to be fairly fluent in English Here's a link to a really simple and good diagram from the book http://www.trenholm.org/hmmerk/HMbooks4.html#HRpicwonderful color and wonderful depth of field !