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12-22-2012, 01:56 AM   #1

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Pentax DFA 100mm Macro WR sticky blades?

Any of you have/had the problem of sticky blades with DFA 100mm Macro WR?

There is no visible oil on the blades, but they don't close/open as snappily as those in other lenses.

Aperture is OK at F/2.8 and F/4; but from there on, the smaller the aperture, the more pronounced the overexposure.

I wonder if I should send it to Eric or to CRIS (the lens is out of warranty).

12-22-2012, 04:53 AM   #2
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Hi, SOldBear,

My name is Holger and I just registrated myself in the Pentaxforum.

I have same problem as you - but with a different lens. I own the Pentax 100 mm f=2.8 lens of the A series - a very good lens but unfortunatelly with the sticky blades problem. To me it seems so as if the mechanics is from the pin that transfers the apperture value and the apperture ist linked with a spring and that this spring lost its tension.

But the blades seem to be sticky, too. I tried to get them free by moving the pin that transfers the apperture value very often. There seemed to be little success. At least the apperture closes rapidly - which is OK for just one photo - for the second photo apperture opens again to give way free to get the view through the viewfinder with full apperture - dand this procedure lasts so lang that you get a wrong result for the next photo. I asked Pentax and they told me that they could exchange the blades - but this would be a very expensive job. You could nealry buy a new lens for the money. I solved the problem by buying a used Sigma 105 mm macro which is a nice lens, too.

Best regards
12-22-2012, 10:23 AM   #3

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I just received a quote from Eric. It 's very reasonable. I'll send him the lens after the holidays.
Holger, if you still have the 100mm lens, check with Eric -> link. I'm a repeat customer of his.
12-22-2012, 12:41 PM   #4
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QuoteOriginally posted by SOldBear Quote
Any of you have/had the problem of sticky blades with DFA 100mm Macro WR?
Not till I read your post and checked the aperture, same thing as yours, stiff/dampened action resulting in over-exposure at smaller apertures.

12-22-2012, 08:25 PM   #5
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It Happened to me too, luckily i noticed this problem in the first days, and amazon exchanged for another one.
08-08-2013, 10:05 PM - 1 Like   #6
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I just bought a used one of these lenses, with no warranty of course. It too had sticking blades. But since I'm sort of in electronics & precision mechanics business, I decided to have a go (repairing).. seems that the problem is easy to fix. Thankfully there isn't oil in the blades themselves, but in the mechanics that open them. I'll post a couple of pics when I get home
08-09-2013, 12:22 PM - 4 Likes   #7
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Here you can see the problem, there's some oil getting from the AF drive gears to the aperture control ring. The ring fits snugly between the mount and lens body, so any oil between there will dampen the action.

To fix it, just remove lens bayonet (upside down so that the electrical contact springs don't accidentally get inside the lens), pull up the aperture control ring (at the same time remove spring attached to it) and clean up.. works again

In the pic, aperture control ring has that looong pole that goes to the hole just close to the rear lens element, approx. there where it says "CE" on the lens barrel.
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10-19-2013, 03:46 PM - 1 Like   #8
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So after seeing jaeaetee take the lens apart and reading the post
QuoteOriginally posted by Edzo Quote
I do have the same problem with my Pentax DFA 100 mm f/2.8 WR lens especially on apertures f/11 and up (to f/32). I don't have any problems on f/2.8.
I think I have located this problem today to the aperture pin on the lens. When moving it to "aperture open" it will go back very slowly to the small aperture where the pin on other lenses will go back very quickly.
When pushing the aperture pin somewhat to the outside of the lens you will hear a "click" inside the lens and when you let the pin go, it will go back very quickly again.

Is there someone aware of this problem with the DFA 100 mm WR version?
Probably you will have the same issue?
I did the same.

No Exxon Valdez, no bent or broken parts or scuff marks on anything, just a mystery.
I did experience jamming of the aperture lever while tightening the screws on the bayonet mount when putting it back together. Wiggling the lever while cranking down on the screws took care of it.
End result of the dis-assembly and look-see is a working DFA 100 WR macro with snappy aperture and no answer to why it was sticky in the first place.

Last edited by Ex Finn.; 11-11-2014 at 05:45 PM.
07-17-2017, 05:59 AM   #9

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I recently bought a used DFA 100mm WR that had the same problem. Thanks to this thread I was able to take it apart and clean the oil from the aperture control ring. It definitely is quite an easy fix if you know what you're doing.
07-23-2017, 05:47 PM   #10
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Mine did that right out of the box but after a couple of days of use it stopped and I never had that problem again.

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