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01-19-2015, 11:49 AM   #1
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Stiff focus ring on M 300/4

The focus ring on my otherwise clean copy of the M 300/4 is bit too stiff for my liking. It feels like it has not been used in years and the lubricant stiffened up with age. So I have a couple of questions:

(1) is this lens typically stiff to focus?
(2) Is it likely to improve with use or should I look into a CLA?
((3) any idea how difficult it would be to re-lube it by someone with almost zero experience disassembling lenses?

Thanks a bunch in advance for suggestions.

Andy

01-19-2015, 12:14 PM   #2
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My experience is with the M*300. It was super smooth and exact to focus. Is yours the one with the green star? Perhaps the non-star M300/4 is different in operation but I think the main difference between it and the star model was in the optics.
01-19-2015, 12:14 PM   #3
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If you're lucky, it will improve on its own with use. I had an A-series 35-105mm with an incredibly stiff zoom ring, but after using for a few days, it went back to feeling like new.

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01-19-2015, 12:52 PM   #4
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QuoteOriginally posted by Adam Quote
If you're lucky, it will improve on its own with use.
I will take this answer and cross my fingers . The lens is the green star version. I am still in shock how well proportioned it is, wow.

01-19-2015, 03:26 PM   #5
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If you can manage to get the lens groups out (not too tough on the M series lenses), a quick shot of lighter fluid to the focusing helicals will likely loosen things up without major disassembly.

The other, more dangerous option is to put it in your oven the LOWEST SETTING WITH THE DOOR OPEN for about 10 minutes, then take it out with a towel (it will be hot), and focus in and out 50 times or so. This will melt the hardened grease and redistribute it throughout the helical. Make sure you put it in the oven when it is cold and allow it to heat gradually, or the thermal stress can crack the glass. The other danger of this technique is it can cause the lubricant to liquify and migrate onto the aperture blades, so be VERY careful if you decide to go this route. Come to think of it, you can probably get a similar effect also by blowing on the outside of the focus ring with a hairdryer for several minutes, without as much risk to the glass and plastics.....

---------- Post added 01-19-15 at 03:28 PM ----------

The helical threads on a zoom ring are much wider and less prone to binding than those on a focus ring. IIRC, on the A 35-105, they are barely lubed, with most of the work being done by delrin bushings. Unfortunately, this might not translate to success in this particular scenario.

QuoteOriginally posted by Adam Quote
If you're lucky, it will improve on its own with use. I had an A-series 35-105mm with an incredibly stiff zoom ring, but after using for a few days, it went back to feeling like new.
01-19-2015, 05:58 PM   #6
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QuoteOriginally posted by dcshooter Quote
get a similar effect also by blowing on the outside of the focus ring with a hairdryer
Thanks dcshooter, this sounds like something I can try, appreciate the tip.
03-07-2015, 11:10 PM   #7
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Update: I sent the *300/4 to a well-known Pentax repair person for a re-lube, the lens just arrived back. The focus is smoother now, but still 2-3 times more stiff than any of my M lenses. I am rather confused by this. Wouldn't a complete re-lube make the focus buttery smooth and not-stiff. When I say "stiff", I mean it is impossible to quickly turn the focus ring with one hand while the lens is mounted and the camera is at eye level, something that I've come to expect from all my lenses, no matter how old. This really bums me out
03-08-2015, 05:54 AM   #8
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Depends on the weight of the grease used and the width and number the helical threads. It could be that the repair person uses the same grease across all lenses and that it is not particularly well-suited to this lens.

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