Manual variable aperture zoom on a digital Pentax

Started 2 months ago | Questions thread
OP alex_virt Senior Member • Posts: 2,395
Re: Manual variable aperture zoom on a digital Pentax

MightyMike wrote:

alex_virt wrote:

Can anybody explain to me how a manual A-series zoom with variable max aperture behaves on a digital Pentax camera?

For example, I have an F3.5-4.5 zoom.

Do I understand correctly that the camera doesn't know the actual aperture and treats the lens as a constant F3.5 zoom and underexposes at the long end?

If I set the aperture in camera to F4.5, will it remain F4.5 through the zoom range and become wide open at the long end? Or will it remain stopped down to the actual aperture of F5-something at the long end?

If set to a small aperture, e.g. F8, will the actual aperture remain F8 through the zoom range?

I'm confused...

Its an A-series lens, the camera therefore knows the aperture, the camera also therefore knows when the aperture is not F3.5 anymore when you zoom. So set the camera to F3.5 at the wide end, zoom the lens and watch the aperture change on the back of the camera (there is an off chance you may have to tap the shutter button to see the change) That said, when set to F4.5 its F4.5 regardless of what zoom position you're at, ditto for F8.0.

On my KP it doesn't change and remains F3.5 at both ends.

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