Yes, JC, I noticed the focus shift too. And you're absolutely correct that the point of main focus stays pretty sharp as this lens is stopped down, although it's so close to being out of focus it doesn't give much room for error.
It's almost exactly the same on another V2 Summilux I tested.
With other lenses, like a Noctilux, the shift was so severe that the original focus point went completely out of focus as I stopped down, and refocusing would have been required to keep the subject sharp.
I haven't done the tests at any other distance.
Almost all the lenses I checked had a very narrow band of focus in front, and much more in focus behind the object I was focusing on. This might be good for landscape shots, but I've been doing more informal portraits, and for that I'd much prefer if the situation were reversed, i.e., with the thing I'm focusing on at the back of the focal field. That way, if I'm focusing on someone's eyes, they would be the last thing in focus which would throw the ears and the background more out of focus, kinda like the way traditional large format portraits looked.
I think a practical solution for someone like me might be to have the lenses optimized or collimated at one stop more closed down than the maximum aperture. Maybe then the subject would be at the rear of the focus field when shooting wide open and it would give a little more lattitude when stopping down.
Or maybe my rangefinder in the camera is off a bit and needs adjusting.
Hi Brusby,
Your test @4 feet do show a focus shift - about 2 inches at f4 which is a lot . By chance, thanks to the DOF, the point of focus is preserved at any aperture. The DOF seems to extend from about -1 inch (regarding the point of focus) to the end of the DOF region, which is very usable once this behavior is known.
Did you do made some tests at other distances @f1.4 ? It could be interesting to compare with my findings on another summilux lens.
Regards,
JC