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01-07-2013, 08:44 PM   #1
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SMC Pentax-A 70-210mm F4 question

I am new to Pentax, with a K-5 II and purchased an older SMC Pentax-A 70-210mm F4 Zoom lens. While the lens appears to be in excellent shape, I have been unable to figure out how to unlock the lens barrel so it will zoom between the 70 & 210mm range. It is locked at the 70mm end (I am assuming that the barrel zooms longer for the extended range).

One other thing, to mount & use the lens I followed the instructions I found here to mount it on the camera:
Shooting manual lenses on Pentax DSLRs robertsdonovan.com
Everything went fine, except I did not get a prompt on the rear LCD display to enter the focal length used when I turned on the camera. SR is turned on. I will read over that again, error is probably something I am not doing. I can change the aperture and exposure appears to correct.

Any help with releasing the barrel?

Will

01-07-2013, 09:19 PM   #2
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You are likely in Macro mode. Turn the focusing collar to move the green Macro label away from the 70 label (turn the focusing collar clockwise when looking at it from the back of the lens.) That should allow you to zoom by pushing/pulling the focusing collar.
01-07-2013, 09:39 PM   #3
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I have rotated the focusing ring both directions until it stops and still can not pull the collar out. I tried pulling with a lot of pressure, but no joy. From fully compressed it will pull out about 1/4" before stopping. When stopped I can just see the very bottom of the 150 markings. You mention the 70 label, I can't see that at all. At the bottom below the collar is the 210mm label, so I assume the 70 must be hidden under the collar.
01-07-2013, 09:44 PM   #4
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I've never had that problem with mine. It would appear that you have a defective lens. The 70mm marking is indeed found when the collar is fully extended.

01-07-2013, 09:59 PM   #5
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QuoteOriginally posted by enoxatnep Quote
I've never had that problem with mine. It would appear that you have a defective lens. The 70mm marking is indeed found when the collar is fully extended.
Thank you for the help, I think I will just put it away for the night and look at it again in the morning.
01-07-2013, 10:12 PM   #6
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Agreed - something is jamming the lens. I haven't had this lens apart before but you may be able to find something on the net. Typically, the A-lenses have some screws under the rear edge rubber collar grip.

This group is frequented by some knowledgeable guys: Favorite Classics / Camera & Repair Articles
Another one: Manual Focus Forum

Keep us posted.
01-07-2013, 10:31 PM   #7
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I had this happen with a lens that I was given when I was young and foolish. It welded itself to the 80mm end of a 28-80 lens I think. One end, anyway.

My solution back then was to put the lens in a vise (padding it so it didn't scratch it, but held it firm) and grab the zooming end with one of those things that opens lids of jars and twist. It budged! Apparently the lens had been hit and was slightly "out of round" so to speak.

I'm not recommending this, because my older self realizes that more could go wrong than right...but it did work back then, and I still have the lens - and the mechanism is still very stiff! So, if you're desperate...
01-08-2013, 04:17 AM   #8
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QuoteOriginally posted by Wingincamera Quote
I have rotated the focusing ring both directions until it stops and still can not pull the collar out
When you say "collar" you are referring to the focusing ring- zoom ring combination, right? this is a one touch zoom known for zoom creep not jamming.
QuoteOriginally posted by Wingincamera Quote
I am assuming that the barrel zooms longer for the extended range
No the barrel does not get longer when zooming in or out, it only gains length when focusing close in.

Cheers.

p.s. lens zoomed to 70mm and 210mm.


Last edited by Ex Finn.; 11-11-2014 at 05:46 PM.
01-08-2013, 11:12 AM   #9
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The second photo is what the lens looks like. I can only pull the zoom collar out to the bottom edge of the "150" markings, about 1/4 inch.
01-08-2013, 03:06 PM   #10
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QuoteOriginally posted by Wingincamera Quote
The second photo is what the lens looks like. I can only pull the zoom collar out to the bottom edge of the "150" markings, about 1/4 inch.
Then she is unfortunately broken, maybe someone here on the forums has tackled a repair on one of these lenses.
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