Is Panasonic 12-35mm II parfocal?

Stejo wrote:

left eye wrote:

Stejo wrote:

left eye wrote:

The issue with many constant aperture lenses (12-35mm f2.8 mk1) is that they are actually not intrinsically constant aperture (this is almost impossible to achieve optically). Instead the wide end is actually brighter than f2.8, but the lens iris automatically stops it down to f2.8, then as you zoom in, and the lens optically becomes darker the iris opens to compensate - so creating the illusion of a constant aperture lens. Even when in full manual mode the lens will automatically keep it's aperture at f2.8 by adjusting the iris.

In video this can be a pain, as the adjusting aperture clicks and abruptly affects the exposure - with a flicker. The 12-35 f2.8 mk1 (maybe also the mk2?) has this annoying behaviour, as do many other lenses.

Variable aperture lenses, such as the Leica 12-60, show no such flicker of the aperture, and darkening is not noticeable when zooming in. It's my number 1 video lens, perfect, so glad I bought it, glad to see the back of my flickery 12-35mm f2.8!

That's not how constant aperture zooms work in principle.

To achieve constant aperture when zooming in and out the physical size of the diaphragm does not change. What changes is the effective aperture, also known as the entrance pupil, which is the appearance of the aperture as viewed through the front element. It's a simple magnification change by shifting the elements around.

If you got a source showing that the 12-35 is different in this regard, I'd like to see it.

why does the aperture click and cause flicker when zooming in / out?

For any number of irrelevant reasons. That's not an indication of anything.

Again, if you got a source, schematics, anything that backs up the claim that the lens actually plays with the physical diaphragm to maintain constant aperture, please do post them. It would be an entertaining read.

...or entertaining to watch?...

https://www.youtube.com/watch?v=u2vjROGkgUA

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