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I am facing problem with a Nikon AF 50mm ƒ/1.8 lens which is attached to a Nikon D7100. Although I can change the aperture from the camera (in M mode) it seems that it is not changing in photos. What I mean:

The aperture is locked in ƒ/22 and I am able to select all values (1.8 – 22) from the camera switch. The problem is that in every shoot the photos have exactly the same aperture, ignoring my initial selection in camera. Unfortunately I don't know which is the selected one. If I check the info of each photo I can see the ƒ-number that was selected; however, taking photos from 1.8 to 22 (in the same light conditions and without to change ISO or shutter), all photos appear the same! Which means that the aperture is not changed!

If I select the Auto mode I can see the aperture that the camera selects however, my photos are overexposed, which means that something is going wrong with the aperture selection.

Can anyone help about what to check in this lens? All other lens are working properly so I don't expect problems in camera.

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Assuming all other potential issues are eliminated (and it sounds like you've done a good job of making sure of that), I would check the following:

  1. Does the aperture close on its own smoothly? Almost all Nikon F-mount lenses (including this one) have a mechanical linkage to the camera body. So you can easily check the aperture's action by taking the lens off the camera body, and using your finger to manually move the aperture linkage lever. It should move counter-clockwise (when looking at the rear of the lens) (causing the iris to open all the way to ƒ/1.8), and the internal spring should return to the clockwise position (returning the iris to the stopped-down setting indicated on the aperture control ring). It should rotate very smoothly, and not require any force other than the obvious pressure against the spring.

    The aperture linkage lever is shown by the yellow arrow in the image below (ignore the red arrows; I copied this image from another answer on this site):

    Nikon F-mount lens with yellow arrow showing aperture linkage lever

  2. Closely related, is the aperture linkage lever bent, or worn? It's very short, and usually won't have much opportunity to be bent. But it's possible that there is a slight bend in the camera's aperture linkage lever that engages the one on the lens. It could be very slight, and due to mechanical tolerance mismatch, it's possible that your specific camera body and this specific lens don't physically engage together apropriately, while still not exhibiting any aperture problems with your other lenses.

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  • \$\begingroup\$ You are right...The problem is related with this lever with the yellow arrow in your print screen. I removed the lens from the body and i pull this lever with my finger to the opposite direction (totally open towards the F1.8). Unfortunately the lever was not return to its initial position but stacked in F1.8.. It was needed to touch it again in order to be back to closed position - F22 Any idea how to fix this? Shall i drop gun oil inside the lever using a syringe? Or i need to lubricate the diaphragm? \$\endgroup\$
    – jockler
    Commented Oct 31, 2019 at 19:13
  • \$\begingroup\$ Do not add any lubricant or fluid to the lens. You'll have to determine if the friction is caused by a slightly bent lever (in which case you might be able to gently bend it straight with precision pliers), or if the aperture blades themselves are rubbing together or sticking. If the latter, then you probably ought to send it in for repair (but that's probably more expensive than just finding another used 50mm ƒ/1.8D somewhere). You can try disassembling the lens and seeing if you can clear/clean the stickiness, but only if you're prepared to write off the lens completely. \$\endgroup\$
    – scottbb ♦
    Commented Oct 31, 2019 at 19:20
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Another possibility is the Custom Command Dial menu setting for aperture... it can be set to "aperture ring" for use with lenses that have the ring.

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  • \$\begingroup\$ Great thinking. I completely forgot about that custom setting. \$\endgroup\$
    – scottbb ♦
    Commented Oct 31, 2019 at 16:15
  • \$\begingroup\$ How can i do this? Do you remember the path inside the menu? \$\endgroup\$
    – jockler
    Commented Oct 31, 2019 at 19:13
  • \$\begingroup\$ If the lever is sticking or the spring is loose/broken then you don't need to worry about the menu option... it's not the issue. Along with what Scott suggested; it is not entirely uncommon for the return spring to become disconnected. \$\endgroup\$
    – Steven Kersting
    Commented Oct 31, 2019 at 20:40

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