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07-15-2013, 03:40 AM   #1
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smc PENTAX zoom 70 210 blocked aperture

Hi there,

Just some days ago I realized that my beloved lens, the smc PENTAX ZOOM 1:4 70-210mm, had an aperture problem.
The aperture sticks to the maximum (f/4) whatever I do. I'm using this lens with both my DSLR (K200D) and the SLR (ME super). The internal mechanism seems ok, for two reasons: 1) Having the lens unmounted, rotating the aperture ring shows the diaphragm properly moving; 2) With the lens unmounted, if I move the "little lever" on the internal side of the lens (the one with gets attacked to the camera) which command the aperture, I can see the diaphragm moving properly.
The problem comes when I mount the lens on a camera.
I realized this with my DSLR: by setting the "A-mode" I no more can control the aperture, which sticks to maximum and mislead the exposure meter. For example, if I digitally set F/32 and read the exposure, the camera calculates the light as if the shot will be taken at F/32, but when shot I get an aperture of F/4 and a overexposed photo. The problem exist also when manually regulating the aperture (not using the "A-mode").
I haven't tryied yet if the problem exist also on my SLR, since I need some time to develop the film.

Does anyone have any tip for this? Any help would be so appreciated! Thanks in advance!

07-15-2013, 04:38 AM   #2
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Hi Alex
Check this article. https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
Hope that solves your problem.
Regards,
Mark
07-15-2013, 04:58 AM   #3
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QuoteOriginally posted by alexlomba87 Quote
Hi there,

Just some days ago I realized that my beloved lens, the smc PENTAX ZOOM 1:4 70-210mm, had an aperture problem.
The aperture sticks to the maximum (f/4) whatever I do. I'm using this lens with both my DSLR (K200D) and the SLR (ME super). The internal mechanism seems ok, for two reasons: 1) Having the lens unmounted, rotating the aperture ring shows the diaphragm properly moving; 2) With the lens unmounted, if I move the "little lever" on the internal side of the lens (the one with gets attacked to the camera) which command the aperture, I can see the diaphragm moving properly.
The problem comes when I mount the lens on a camera.
I realized this with my DSLR: by setting the "A-mode" I no more can control the aperture, which sticks to maximum and mislead the exposure meter. For example, if I digitally set F/32 and read the exposure, the camera calculates the light as if the shot will be taken at F/32, but when shot I get an aperture of F/4 and a overexposed photo. The problem exist also when manually regulating the aperture (not using the "A-mode").
I haven't tryied yet if the problem exist also on my SLR, since I need some time to develop the film.

Does anyone have any tip for this? Any help would be so appreciated! Thanks in advance!
@MackJering- not too many folks have prized lenses that they haven't been using successfully, also this is an A-series lens. With the exception of auto-focus, you have full functionality the same as digital body specific lenses.

@alexlomba87- move the aperture ring off and on the 'A' setting on your lens and make sure the A contact pin on the lens is properly retracting and extending. If it doesn't extend when on the A setting, it won't touch the recessed counterpart on your camera body. It also won't hurt to polish all the contacts on the lens and bodies with a rough cloth dampened with isopropyl alcohol.
07-15-2013, 06:10 AM   #4
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Sounds like a sticky aperture to me.

07-15-2013, 06:24 AM   #5
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QuoteOriginally posted by MarkJerling Quote
Hi Alex
Check this article. https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
Hope that solves your problem.
Regards,
Mark
Hi Mark, thanks for your replay. Anyway, I've been using both my old Pentax zoom and my K200D for a while now (some years), and I think I really do know how to set them up. However I took a look to your well-written guide, but unfortunately It wasn't helpful. Thank you anyway.
07-15-2013, 06:37 AM   #6
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QuoteOriginally posted by JimJohnson Quote

@alexlomba87- move the aperture ring off and on the 'A' setting on your lens and make sure the A contact pin on the lens is properly retracting and extending. If it doesn't extend when on the A setting, it won't touch the recessed counterpart on your camera body. It also won't hurt to polish all the contacts on the lens and bodies with a rough cloth dampened with isopropyl alcohol.
Hi there, thanks for your reply. That seem interesting; I've already thought about cleaning pins but I'll give it another try. Asap I'll check if the contact pin is properly retracting and extending ad you said; I wonder what I can do in case not. The thing is, if the pin is not extending the camera should show Like the "F--" signal on the display, am I wrong (similarly ad when not setting up the "a-mode" on the aperture ring) And that's not the case; more, even setting up e.g. F/32 on the aperture ring (no"a-mode") will result in a photo with an f/4 apeture.
07-15-2013, 06:41 AM   #7
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QuoteOriginally posted by VisualDarkness Quote
Sounds like a sticky aperture to me.
Hi, thanks for the reply. Is that a common probleM? I was wondering that. Strange thing is that the diaphraghm is actually moving properly when the lens is not attached to my Dslr.
07-15-2013, 07:10 AM   #8
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QuoteOriginally posted by alexlomba87 Quote
Hi there, thanks for your reply. That seem interesting; I've already thought about cleaning pins but I'll give it another try. Asap I'll check if the contact pin is properly retracting and extending ad you said; I wonder what I can do in case not. The thing is, if the pin is not extending the camera should show Like the "F--" signal on the display, am I wrong (similarly ad when not setting up the "a-mode" on the aperture ring) And that's not the case; more, even setting up e.g. F/32 on the aperture ring (no"a-mode") will result in a photo with an f/4 apeture.
Unless the lens was banged around recently, my bet is on the A-pin not making good contact. And the most typical reason seems to be that the aperture ring is not fully locked in the A-position.

Do keep in mind that you CAN manually set the aperture on the ring. At that point you will have the equivalent of a M-series lens and will need to follow Mark's advice.

Or there is a 3rd option ..... you can plug the A contact point on your camera body and make it think ALL lenses are A-series lenses ....
https://www.pentaxforums.com/forums/pentax-camera-field-accessories/113756-pk...ml#post1965512

(pictures to go with the text are a couple posts further down) As you can see, this is how I handle mounting my A-series and even DA lenses on my macroconverter or bellows unit and retain full exposure capabilities. I have seen no reason yet to remove the plug.

07-15-2013, 07:38 AM   #9
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QuoteOriginally posted by JimJohnson Quote
Do keep in mind that you CAN manually set the aperture on the ring. At that point you will have the equivalent of a M-series lens and will need to follow Mark's advice.
Hi, thanks a lot for your extensive answer. I'll surely consider anything you said and I'll let you know asap. Anyway, I just wanted to point out that even manually setting the aperture on the ring and allowing my k200d to shoot with the right configuration, the aperture sticks to the max. So if I set the ring to F/32 I still have the same aperture that I have when setting the aperture ring to F/4. Sorry if I'm repeating or being unclear, I thought I've already said that., I just want to be sure I'm correctly explaining the situation. Sorry also for my poor italian-english and typos
07-15-2013, 10:39 AM - 1 Like   #10
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The aperture lever at the camera end of the lens may be slightly bent in or out (not sure which). Look at it. If nothing obvious try pushing it one way and if NG then the other way.
07-15-2013, 11:38 AM   #11
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It sounds like some mechanical interference. Off-camera, set the ring to f32. The lever should move the blades fully open. Release the lever and the aperture blades should snap shut just about in the blink of an eye. On the camera, the blades have no trouble being held open, but they appear to not close properly.

You could try looking into the lens when it's on the camera. Set the camera to f32 and using the optical preview. The blades should close. If they move slowly, photos with short shutter speeds will be very overexposed. Longer shutter speeds will have less overexposure, as the blades have more time to eventually get to the right spot.
07-15-2013, 11:56 AM   #12
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QuoteOriginally posted by dms Quote
The aperture lever at the camera end of the lens may be slightly bent in or out (not sure which). Look at it. If nothing obvious try pushing it one way and if NG then the other way.
GREAT! Problem solved! Thank you so much!
The bent was actually slight, and I didn't think that it could be the problem. I really can't figure out how could I bent the lever, also I would never notice that if I had not been told!
Thanks again also to everyone who answered!
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