Sigma 150-600 Contemporary question.

[Shawn]

First off, I love this lens, it sits side by side with the redcat on an AM5N, takes wonderful images, but through a Nikon Z6. The Nikon being full frame does not really utilize the higher end of the lens . Question is as this lenses Aperture is governed by the camera obviously wide open for astro. What happens if I plug in a dumb cooled ASI camera..Wheres the default, does it just stay where I left it last?....Ive been through the Sigma FAQ's and all the what do all these flashy buttons do on the side ?. and which end plugs onto the camera type stuff .. But nothing comes to light. anyone out there that can shed some aperture on this ???


Cheers
Shawn

[rising (Craig)]

I don't know anything about a Nikon Z6, but Google tells me it has a mechanical (rather than electricial) aperture. If it were electrical like Canon, you would probably be sunk with no option to control aperture unless somebody has produced some adapter with electronics in it..

I have Sony A-Mount lenses which also have a mechanical aperture. When the lens is removed from the camera, the aperture closes. It is spring loaded. If you look at the rear of the lens there is a little lever you can push to adjust aperture. I expect Z-mount lenses to be similar. Just shine a led torch down the front of the lens to confirm the aperture is closed off camera.

That means it should possible to make a purely mechanical adapter with aperture adjustment. Maybe such an adapter is available if the flange/sensor distance is large enough (may be an issue on mirrorless cameras). I have made a 3D printed one for A-mount by adapting a design from Thingiverse. Printed in PETG-CF. Yet to see how well it works in practice, but the aperture ring on the adapter works fine.

[Shawn]

Thanks Craig, I will take a closer look , see if I can work it out for myself, I dont really want to sell it , but if I have to well the war office says I already have too much stuff. You know what I mean...

[SteveInNZ2 (Steve)]

I just had a play with my 150-600C as your question made me curious. This was with a Canon 80D.
If you turn the camera off, the aperture returns to fully open. If you leave the camera on, depress the aperture preview button and undo the lens, the aperture stays at the position set on the camera.
If you put the lens back on the camera, the aperture returns to fully open. That happened even if the power switch was off (which I wasn't expecting).
I tried plugging the lens into dumb extension tubes and into a (smart) EOS-Sony adapter and the aperture didn't change.
So, for my camera/lens I would expect to be able to set the aperture with the camera, remove it with the power on and preview pressed and use it with my astro camera and dumb adapter.

I would expect the Nikon version to behave the same but that's not guaranteed.


Steve.