Is Panasonic 12-35mm II parfocal?

Stejo wrote:

kolyy wrote:

Stejo wrote:

kolyy wrote:

Come on, it does. There is the video above and my copy does exactly the same. I have just looked at it. And it is a well known phenomenon, I knew about it when I bought the lens a couple of years ago, so I was not surprised. You should really listen a bit more to people who own the lens and know something about it.

I don't own the lens to verify right now, but I've used it on multiple occasions and never noticed anything of the sorts. Furthermore, there's a bunch of people commenting on the youtube video above that they don't have this problem or that they have it under certain circumstances etc.

Did you consider the possibility that there's some sort of bug or defect with your particular unit or camera combination? Opening and closing the diaphragm during focal length changes is simply not part of constant aperture zoom designs.

If it happens for your lens while you're in manual exposure mode, it's not normal. If it happened with every 12-35 copy, I believe I would have noticed it myself or it would be well known. You understand my skepticism.

Still, I'm not saying it's impossible, cause you never know. But it's extremely unlikely. And if you're certain it is so, feel free to prove it. I'd be happy to know.

Two of you claiming the same thing now has me actually in doubt. I'll see if I can find any leftover copies tomorrow morning to check it out.

You are really stubborn, aren't you?

Opening/closing of the diaphragm might not be your typical design of a constant aperture zoom lens, but it is most certainly part of the design of the 12-35/2.8. Or do you really suggest that my lens is stopped down to less than F2.8 at the wide end all these years and I somehow didn't notice? I suggest you take a close look how the lens works when you have it in your hands next time. The flicker while zooming might not be always noticable, there are just four jumps in the whole range.

https://www.dpreview.com/forums/thread/3752038

https://www.mu-43.com/threads/12-35mm-x-constant-aperture-through-zoom.32435/

http://www.dvinfo.net/forum/panasonic-lumix-g-gf-gh-gx-series/523874-gh4-image-flicker-when-zooming-12-35-lens.html

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

https://www.youtube.com/watch?v=i7OfxuwZ_9o

https://www.youtube.com/watch?v=B3fipANbTlI

I most certainly am but yes, you are right. How I never noticed any of these discussions baffles me.

Anyway, I dug up optical construction schematics and it's clear there's at least one moving zoom group behind the diaphragm which is responsible for what's happening. Possibly two. Hard to tell. This is such a puzzling design for a mere 3x video oriented zoom. Seems they were obsessed with keeping size down.

And apparently they maintained the same design for version ii, only this time they oiled up the aperture blades a bit better and toned down adjustment speed so it doesn't click all over the place.

I lost my confidence in constant aperture lens's, maybe some are ok, but some like the mk1 12-35 f2.8 should not have been pushed out for video oriented cameras such as the GH4 etc. Shocking really, and I can understand those who have not owned it would think it impossible for the aperture to be jumping while zooming, but that is what it does. I almost think it's not fit for purpose. An expensive lens also.

Not sure about the mk2, I wouldn't take the gamble.

Very glad to have now got the Leica 12-60 variable aperture, no clicking no flicker, just beautifully zooming in. No noticeable darkening either when zooming in.