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09-19-2015, 10:25 AM   #1
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Slow Aperture on D-FA 100mm

Hello folks.

I discovered today that the aperture lever on my D-FA 100mm Macro is quite slow. Using a flashlight i can not see any oil or other foreing substances on the Aperture blades themselves. I believe it is mechanical friction in the lever mechanism. It is not sticky, just slow.

I have removed the mount of a MF lens before (Auto Chinon 135mm F2.8) with no trouble putting it back together, but I'm a bit hesistant to do this on an AF lens. Do anyone have experience in opening up an AF lens with WR?

My intention is to very carefully lubricate the moving parts in the lever mechanism.

Best regards Tim

09-19-2015, 10:40 AM   #2
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Typically the advice I see on manual focus lenses is to carefully clean with naphtha or similar solvents and then relubricate. Not sure if naphtha is ok with modern lenses due to the plastic parts. Someone else should know more details.
09-19-2015, 10:58 AM   #3
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Before proceeding timcatn, check if the lens needs any aperture lubricant at all. I've heard that lubricants leaking from focusing or zoom mechanisms (in case of zoom lenses) of lenses can actually stick up the aperture mechanism. I hope you success in whatever you decide to do
09-19-2015, 12:06 PM   #4
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The oil is not always visible. Naphtha has been fine for all the FA lenses I've worked on. It's recommended to remove both the front and rear groups in order to clean the blades

On AF lenses like this, there are several small contact springs that can easily get lost/misplaced. If you decide to take the whole mount off, be very careful while removing it and take a picture of the spring positions. You might actually be able to get by on this one by just removing the matte black baffle, which should give you enough room to remove the rear group.

The front group might be tricky due to the how deeply recessed it is. Not sure about the 100, but on the 50mm, there is a conical front baffle that you have to remove prior to taking out the group.

---------- Post added 09-19-15 at 12:08 PM ----------

Also, if it does turn out to be the lever, clean the bearing surface off with naphtha and apply one drop, NO MORE, of light machine oil to re-lubricate it.

09-19-2015, 11:17 PM   #5
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Sometimes the aperture lever is slow it is because it is bent. Compare it to one of your other lenses. Generally it gets bent toward the middle of the lens. If it is bent in it generally is not too difficult to bend it back and things will move smoothly again.
09-20-2015, 02:48 AM   #6
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Mine has the same problem, and i did some searches in the past on the forum and found a couple of thread mentioning the same issue. It seems that it is a relatively common occurrence with this lens

This thread for example

contains some useful information.

I have not attempted to repair (or get repaired) mine, since actual problems (overexposure) only show up at fast burst rate and very small apertures (past f/16), however when operating the aperture lever by hand it is evident that it is not as snappy as it should be.
09-21-2015, 06:47 AM   #7
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Original Poster
Thanks for the tips everyone.

I ended up going for it. I removed the lens mount. I could not see any errors so i slightly moved the starting position of the lever. Effectivly tightening the spring a small amount. The drawback of this is of course that i might have skewed the f-stops slightly (depening if it was correct to begin with). Will test when i get home from work. The operation was fairly simple and took around 30min.


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