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11-22-2009, 07:21 AM   #1
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DA 12-24mm stiffness

If I have the distance set to infinity then the zoom ring sticks at 15mm (focal length) if coming from 12mm, or 19mm if coming from 24mm (narrowest field of view).

If I have the distance set to 1 Metre then the zoom ring feels a bit stiff but I can rotate it completely either way.

If I have the distance set to 0.3 Metre then the zoom ring turns freely with no resistance felt. This is how it used to be at any focus distance until one day last winter. At first I just put it down to the cold but the problem never really cleared up.

The workaround is so simple: turn the focus ring to close-up, zoom then auto focus - that it doesn't justify my parting with my favourite lens whilst it's getting serviced.

I suspect lubrication may be at fault but I'm rather hesitant at removing five tiny crosshead screws from the rear of the lens in case springs or other small parts leap out at me. I do have experience repairing laptops etc.

Does anyone know if it's safe to remove these 5 crosshead screws? There's also a recessed slotted screw which could well be a factory adjustment I wouldn't want to mess with.

11-23-2009, 08:51 PM   #2
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Tough question.
Indeed this doesn't seem quite right, but due to the selective nature of the 'sticking' and rough turning of the zoom ring, it may be a little more complicated than just a global lubrication issue.

I'd not be fooling around with the lens's internal mechanism unless you know what you're doing, but if you're game, do share your experience with us!
11-24-2009, 06:10 AM   #3
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QuoteOriginally posted by Ash Quote
Tough question.
Indeed this doesn't seem quite right, but due to the selective nature of the 'sticking' and rough turning of the zoom ring, it may be a little more complicated than just a global lubrication issue.

I'd not be fooling around with the lens's internal mechanism unless you know what you're doing, but if you're game, do share your experience with us!
I'll stick with the workaround!
03-25-2010, 01:21 PM   #4
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QuoteOriginally posted by henniker Quote
I'll stick with the workaround!
Today I was considering buying the Sigma nearest equivalent- 10-20mm. I felt brave enought to remove 6 tiny crosspoint screws from the rear of the Pentax 12-24mm lens. Don't try this!

Tiny gold electrical contacts and springs sprang out and one landed on the carpet. A tiny curved polythene spacer came out too. The rear black plastic cover had fractured round the minute grub screws holding it on.

With careful perseverance I managed to reassemble the contacts and screw down the rear silver metal ring. I tested the lens in the K7 and it worked as before. The zoom ring still sticks until I change to a closer focal length.

I've ordered the Sigma 10-20mm lens and once I get it I'll send the Pentax one for repair. It was too expensive to not have it working properly.

03-25-2010, 01:49 PM   #5
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QuoteOriginally posted by henniker Quote
Today I was considering buying the Sigma nearest equivalent- 10-20mm. I felt brave enought to remove 6 tiny crosspoint screws from the rear of the Pentax 12-24mm lens. Don't try this!

Tiny gold electrical contacts and springs sprang out and one landed on the carpet. A tiny curved polythene spacer came out too. The rear black plastic cover had fractured round the minute grub screws holding it on.

With careful perseverance I managed to reassemble the contacts and screw down the rear silver metal ring. I tested the lens in the K7 and it worked as before. The zoom ring still sticks until I change to a closer focal length.

I've ordered the Sigma 10-20mm lens and once I get it I'll send the Pentax one for repair. It was too expensive to not have it working properly.
You've learned the first lesson the hard way.. Another lesson you may have saved yourself from learning is you can't just use ANY lubricant on a lens mechanism. Improper lubes will break down and travel within the lens, to the blades, to the inner glass surfaces, and anywhere else that one might not think of.

It's only a couple weeks old but I'm not seeing similar behaviors in mine. Service is definitely in order.

Good luck..
03-27-2010, 09:00 AM   #6
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I'm guessing that a fragment of plastic from the cracked rear cover may be causing the obstruction to the zoom mechanism. I filled in the form on the Pentax contact page Contact - PENTAX U.K. Limited and am awaiting a reply, hopefully with an estimate.
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