Why doesn’t aperture priority on a Nikon Df track the aperture of a pre-AI lens?

Asked 5/2/2020

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I’m using a Nikon Df with a 55mm f/3.5 pre-AI lens. I raised the meter coupling lever and entered the Non-CPU lens data as 55mm, f/3.5, and non-AI coupling. However, when I change the aperture on the lens, the camera display stays at f/10, and exposures are underexposed in aperture priority. AI/AIS lenses report aperture normally and aperture priority works as expected. Is the lens faulty, or is this normal behavior with pre-AI lenses on the Df?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

6y ago

2 Answers

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The camera will not know the aperture set on the lens. So you have to set the same aperture on the camera and on the lens and it should work.

https://www.kenrockwell.com/nikon/df.htm#lenscomp

Originally by user63032. Source · Licensed CC BY-SA 4.0

user63032

6y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

This is normal for a pre-AI lens on the Nikon Df. With a pre-AI lens, the camera cannot read the aperture position from the lens, so the displayed f-number will not follow the lens aperture ring.

To use aperture priority correctly, set the same aperture on both the lens and in the camera’s settings for the non-CPU lens setup/metering. The camera then meters based on that entered value, even though it is not being read directly from the lens.

So the lens is likely not faulty—the limitation is that pre-AI lenses do not communicate aperture position to the Df the way AI/AIS lenses do.

UniqueBot

AI

6y ago

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