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04-19-2012, 12:06 PM   #1
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Aperature ring on Tokina MF

hi guys, i recently found an old Tokina 35-105mm manual zoom lens and took some great pics with it with my K-x. As my first manual I thought they could only be used wide open BUT it turns out that the aperature ring on the lens is broken and stuck on fully open.

There is a small tab inside the lens which I can turn and this closes the aperature and I can then turn the ring to open to full but I cannot use the ring to close it again (should there be two internal tabs, one to close and one to open the aperature?)

Anyway, I'm a bit gutted because I was so happy to have found this lens and it is still VERY sharp (much sharper than my kit lens), but obviously its usefulness is limited now it can only be used wide open. I bought an extension tube the other day specifically for use with this lens before I discovered this fault.

What do you guys think? Should I keep this, try to open and fix it myself () or try and send it for repairs (I'm not sure how much this would cost)

Thanks!

04-19-2012, 12:12 PM   #2
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are you shooting in manual mode? older manual lenses will not stop down unless you shoot in manual mode and use green button metering. In any of the auto modes, you're stuck with wide open shooting only, since there is no electronic coupling between the lens and camera to tell the camera what the aperture ring is set to. For it to communication to happen between older lenses and bodies, it needs a mount that also supports mechanical coupling, hence why the lens mount on the k-x called a crippled KAF2 mount
04-19-2012, 01:38 PM   #3
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Hi Adpo, yes I am shooting manual, but the aperture blades physically do not close. If I physically reach into the lens, push the tab and close down the aperture, I can twist the aperture ring to open the blades but twisting the ring back again does nothing, thus when I attach the lens to the camera, the aperture is fully open.
04-19-2012, 02:38 PM   #4
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Perhaps a return spring has come unattached inside. Taking the mount off should give you access to see better. As always should be warned, those are not tiny philips screws, they're JIS, and can be stripped relatively easily (or so everyone warns) without the JIS drivers.

04-20-2012, 10:28 AM   #5
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Hi pezmaker, I have taken the mounting ring off and i can see that the little tab which controls the aperture indeed has one spring attached quite far down the lens, should there be another attached?

Without further disassembly of the lens, I dont think I can see much wrong as I dont really know what I'm looking for, any thoughts?
04-20-2012, 01:15 PM   #6
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OK after taking the lens apart, and some prodding about and tinkering, I have cunningly (sort of) fixed aperture control using an elastic band. However, a ball bearing fell out when I was taking it apart and now I'm not entirely sure where it goes...

I'm certain it controls the selection of f/stop on the aperture ring and is responsible for the 'clicking' on the ring. Im not sure where to put it before I screw in the mounting ring.

Help please! :-s
04-20-2012, 01:17 PM   #7
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There should be a small hole in the outer edge of the lens casing, where the aperture ring mounts on. I lost mine on a sears 50 F:1.4, fortunately found it back with a magnet. Anyway, I digress. It's on the outer portion of the lens where the aperture ring covers - it should be fairly obvious once you're looking in that area.
04-20-2012, 01:30 PM   #8
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Obviously a different lens, but this is pretty close to where mine was, so it should give you an idea:

http://www.leitax.com/conversion/contax/Planar_8514/DSCF0640b.jpg

04-20-2012, 02:20 PM   #9
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Thanks for the advice pezmaker! I've managed to trap the ball bearing and now the ring works perfectly. The lens is now fully assembled and... it works! T

he movement is not quite as smooth as it was before disassembly but the elastic band works!
04-20-2012, 02:26 PM   #10
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Happy to help! My first "repair" was a Vivitar (same as sears, so who knows) 135 f:2.5 lens that had oily blades. I need to take it apart again and redo it, but once you have one under your belt, the next one isn't so scary.
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