September 24, 2017 at 7:23PM

5

Problem with my Sigma 28-105mm

I just bought a Sigma 28-105mm f3.8-5.6 uc iii.
I'm having trouble figuring out whats going on with the iris. I've connected it with both my c100mkii and my a7sii(via a neewer lens adapter: http://www.neewer.com/imaging-products/lenses-and-accessories/lens-adapt... )

I went into the menu system of the c100 and into the aperture control. It is greyed out (manual) and when I try to select it, it tells me the function is unavailable with this lens.
When I try it with my a7sii, it seems to work initially (the screen dims and brightens as though the aperture is opening and closing) when I have the selector wheel in Full Manual mode (M). Then I hit record and it goes back to whatever it was initially. When I have it in Movie mode the screen doesn't react at all.

Anybody have this issue? The lens was released in 1999. Is it simply that the lens is too old for these newer cameras? Is there a work around? Google has brought up nothing relevant for me.
Anything helps thanks.

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