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04-10-2018, 03:40 PM   #16
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QuoteOriginally posted by deepbluish Quote
Yes, it does ask for FL input.
GB metering doesn’t necessarily make a sound, but it should activate the aperture lever. I have some Takumars that meter stopped down just fine stopped down. Do you get good exposure if you manual close the aperture and meter stopped down?


Last edited by monochrome; 04-10-2018 at 03:46 PM.
04-10-2018, 06:34 PM   #17
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I think you already stated this but is the lens normally stopped down to its set value and pulling the small lever (outside tab as shown in you photo) downwards opens the lens to its full open position? Just trying to isolate the issue to the lens or camera and need to verify if the lens is doing what it's supposed to do.
04-10-2018, 10:59 PM   #18
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A non-A K-mount lens will normally stop down when not mounted on a body. Moving the aperture lever on the lens will open the iris. When you mount the lens on the body the control lever on the body in the neutral position will push the lever on the lens to open the diaphragm completely. You can confirm this by setting the lens to the smallest aperture while off the body and looking through the front of the lens while mounting it.

Possible causes of an "auto" (with lever) K-mount lens failing to stop down:
  1. iris covered with oil that has become gummy or viscous.
  2. lever missing or disconnected
  3. lever bent or misaligned or jammed
  4. non-conductive lens mount

Check (1) by seeing if the diaphragm opens and closes rapidly and consistently. You can test this by running through the range of f-stops and watching the opening and closing of the iris through the front of the lens. This can be done off camera by moving the lever manually. If the diaphragm lags or doesn't open fully or stops down inconsistently then most likely there is oil on the blades. The lens appears to work on the MX body but since the test is so simple no reason to be sure.

Since the lens seems to work on the MX we can probably rule out (2). However due to differences of design and manufacturing tolerances the lever can still be (3) bent or misaligned just enough to miss the lever on the K-1 body. Check to see if it is not bent slightly towards the center of the lens (away from the outside of the barrel.

Have you shot a roll of film recently with this lens to confirm it is giving proper exposures consistently?

Ruling out all 1,2, and 3 leaves us with (4). The dull looking finish of the mount in the photos suggests either the mount is oxidized or even non-conductive. That the K-1 asks for a focal length suggests otherwise. Since it a simple procedure to carefully place a bit of metal foil between the lens and camera to cover the "data" pin I don't see any reason not to try it just to rule out non or poor conductivity as a source of the problem. Just so long as you take care not to drop any foil into the mirror box.
04-11-2018, 01:08 AM   #19
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It's definitely the conductivity. I've put a piece of foil to cover all the pins on the body mount and then mounted the lens. The camera again asked for FL input and when I entered the FL, it reported the lens to be an f1.8 one.

I'm guessing this is just poor conductivity, not complete lack of it. If I understood correctly, if there weren't any conductivity, the body would not ask for FL input. The question is, how can I make the lens more conductive with least trouble. Sandpapering the lens mount a bit? The entire diameter or just one specific section of the mount?

04-11-2018, 01:20 AM   #20
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If you abrade the mount (and you might as well do all of it) a fine polishing agent like Crocus Paper might be best. Take care to remove any particles from entering the lens.
04-11-2018, 09:41 AM   #21
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It reported an f-stop? My non-A lenses don't do that, they show it as dashes, but the stop-down functions normally otherwise. Does the camera/lens combination operate normally with the foil under the mount?
04-11-2018, 02:03 PM   #22
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If the "A" pin is shorted out it will show an F stop. All the pins shorted would be seen as a f/1.7 - f/22 lens and depending how the EV steps for f-stops are set (1/3 vs 1/2 EV steps) it could show as f/1.8

You only need to short the "data" pin which on the camera body is the pin nearest to the screw drive connector or the mount screw at the 6 o'clock position. You can use a brass wire brush or some #400 or finer sandpaper. Just take care to clean up any particles and prevent them from getting into the lens or cameras.

04-14-2018, 05:15 AM   #23
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I am happy to report that sandpapering did the trick. I only sandpapered the part of the lens mount around the data pin and stop-down metering now works just fine.

Thank you all for your help.
04-14-2018, 02:37 PM   #24
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I like a happy ending
04-15-2018, 06:06 AM   #25
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Let's see some sample pictures! I love 28mm primes and am curious how this lens is performing now that it works with the cameras asked about.
11-27-2018, 05:24 PM   #26
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OK, I also have a Petri 28mm F2 that is doing the same thing but also is NOT anodized so I didn't consider the contacts....I'll try sanding it anyway and see if that works!
11-28-2018, 01:52 AM   #27
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You could always try put a bit of aluminum foil over the contact before mounting the lens. Just make the piece of foil big enough that you can keep a finger on it to hold it in place.

Note: You can buy metal foil tape at auto supply/parts and some hardware stores.
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