Help! Lens not stopping down?

<p>Hi guys<br>

I'm having a big problem with over exposure with my old 50mm f/1.8 AF (non-D) lens on my D90. I dial in an aperture but the lens doesn't seem to stop down resulting in an over exposed picture. The meter responds to the aperture setting, but EXCIF allways says f/1.8 regardless.</p>

<p>Have checked with my 18-105 kit lens, and that's fine.</p>

<p>Is this a compatibility issue, or has the lens died? Is it possible something's sticking; its a very old lens that's spent a fair amount of time in storage.</p>

<p>Thanks in advance for any help you can give me........</p><div></div>

<p>Then with f/8 set on the camera in aperture priority.....</p><div></div>

<p>It's definitely *not* a compatibility issue.</p>

<p>Although this lens is not known to be especially prone to oily aperture issues, that might be the problem. Remove the lens from the camera, set the aperture ring to f/22, and then pull the little lever on the back on the lens down with your index finger and release it. Does it instantly return to the rest position?</p>

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<p><em>"but EXIF always says f/1.8 regardless"</em></p>

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<p>Actually, in your second photo, it does say "f/8".</p>

<p>Thanks Michael<br>

It doesn't return at all. Just stays closed down. Feels stiff when I push the little lever back to open it back up. Spring gone?<br>

Oh. It does say f/8 dooh!<br>

Chris</p>

 

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<p><em>"Spring gone?"</em></p>

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<p>Doubtful (spring<em><strong>s</strong></em> (2) in this lens IIRC). If it feels stiff when you pull the lever to open/close it back up, then the aperture blades are almost certainly contaminated with oil and are sticking together. Discontinue using the lens, as sticking blades place undue stress on the camera stopdown lever mechanism.</p>

<p>Unfortunately, it sounds like your lens requires repair.</p>

<p>Thanks for the warning. Will do.<br>

I'm guessing it will be cheaper to get a secondhand D version than repair. Every cloud has a silver lining!<br>

Chris</p>

<p>Just for interest; would it be harmful to use a lens in this state if it was only used wide open?</p>

<p>Since the stopdown lever will not move if you dial in an aperture of f/1.8, it only needs to pull the lens aperture open when you first mount the lens. So there is no repetitive strain on the body mechanism once the lens is mounted and the blades are initially forced open.</p>

<p>Nevertheless, It's probably best not to do so, and I wouldn't recommend it. Too easy to forget you have a malfunctioning lens and set an intermediate aperture by mistake.</p>

<p>Not sure exactly which lens you have, but with the50mm AF-D you have to set the aperture on the lens to the smallest (f22) and lock it in place.</p>

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<p><em>"... you have to set the aperture on the lens to the smallest (f22)"</em></p>

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<p>Not applicable in this case, since if the aperture ring is not set to minimum (f/22) when mounted on a D90, you can't take any photo, let alone an overexposed photo. :)</p>

<p>I have retired the lens, and replaced with a lovely new 50mm f/1.8 D. Better safe than sorry ;-)</p>