Is Panasonic 12-35mm II parfocal?

kolyy wrote:

Sean Nelson wrote:

kolyy wrote:

None of the lenses I have is able to hold the plane of focus very precisely. In particular, you have to fix the focus when zoomed in, otherwise it does not work.

That's true of parfocal lenses as well. You simply can't see enough detail when zoomed out to be sure that the lens is properly focused when zoomed in. It's always been the case for all lenses that you zoom in and focus first if you want to maintain focus across the zoom range.

The test for "simulated parfocal" lenses is this: if you zoom in and focus, does it hold focus when you zoom out and then zoom back in again.

Ok, I don't have any truly parfocal lens, but I think the plane of focus should not shift at all, right? So if I can focus correctly with peak sharpness on my subject, then I should be able to zoom in.

Because with, for example, the 12-35/2.8 the focal plane shifts in a visible way, when I use manual focus with magnification and focus peaking. I have just verified it. When the focus is fixed at 35mm, the plane of focus stays in the DoF until 18mm and the moves out of it. But if I fix the focus at 18mm, I can clearly see the focal plane drifting forwards when zooming in to 35mm. You will always get a blurry image at 35mm if you correctly focus at 18mm, but not vice versa.

That doesn't surprise me.

It seems to me, that some people here don't realise the implications of parfocality and how it was used in olden days, when we had few (or no) focus aids.

I cannot imagine a scenario where you might zoom out to focus, then zoom in, and expect focus to be correct; nobody would ever do that.