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10-12-2009, 09:00 PM   #1
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SMC Pentax-M 40mm F2.8 "pancake" lens

Hi, I purchased the old "pancake" lens while ago, I really like the way photo comes out.
However, the focus ring is very hard to turn, is there anyone who had same problem before? if so, how did you fix it? did you bring into shop to fix?

Or else... is there anyone who has any idea to fix/make it better? Thank you so much in advance, I would be really appreciated if you can help me.

10-12-2009, 09:52 PM   #2
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QuoteOriginally posted by luckinpentax Quote
Hi, I purchased the old "pancake" lens while ago, I really like the way photo comes out.
However, the focus ring is very hard to turn, is there anyone who had same problem before? if so, how did you fix it? did you bring into shop to fix?

Or else... is there anyone who has any idea to fix/make it better? Thank you so much in advance, I would be really appreciated if you can help me.
Sorry, can't help you. To my experience, stiff focus ring is very rare on Pentax lenses, probably due to a good design. Is there any sign on the lens that suggest it may have taken a hard hit?
10-13-2009, 08:31 AM   #3
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QuoteOriginally posted by luckinpentax Quote
Hi, I purchased the old "pancake" lens while ago, I really like the way photo comes out.
However, the focus ring is very hard to turn, is there anyone who had same problem before? if so, how did you fix it? did you bring into shop to fix?

Or else... is there anyone who has any idea to fix/make it better? Thank you so much in advance, I would be really appreciated if you can help me.


I find that if I try to turn it using pressure from one finger I can't get it to turn at all. If it use two fingers (one on each side of the focus ring) it works fine. This is the case on many of my quick-shift lenses.

EDIT: oops, I thought this was about the DA 40.

Last edited by deadwolfbones; 10-13-2009 at 09:28 AM.
10-13-2009, 09:02 AM   #4
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I recently found a used M40, and yes, my copy is fairly stiff on the focusing ring.

Who knows how it was treated, how much dust ended up inside?

10-13-2009, 11:24 AM   #5
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As this lens is so short the helix for the focus mechanism will also be unusually short. In order to get the same level of damping as their other MF lenses, pentax may have used a different grease. It is quite possible that this will have aged differently from their normal grease and thickened making the focus stiffer.
If the focus is stiff but smothe then viscous grease may well be the cause and it should be possible to dismantle the lens, clean the old grease off and re-lubricate. I have cleaned an re-lubricated several lenses (usually because they were gritty and full of sand) and have not encountered any problems.
10-14-2009, 05:40 AM   #6
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I have this lens and I don't remember a particularly stiff focus ring. I will have to check it out when I get home.
10-14-2009, 09:39 AM   #7
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Just checked mine. It wasn't significantly harder to turn than any of my other MF Pentax lenses. Due to a lack of traction on such a tiny ring, I couldn't effectively control it one/two fingered next to eachother while , but with pinching across the lens, there was a smooth resistance equal to my M50/f2.

Reading back up the thread, I guess it is comparable to the quick shift on DWB's DA40, haha.
10-14-2009, 10:42 AM   #8
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I have this one - I seem to manage it with one finger quite comfortably...

10-14-2009, 10:05 PM   #9
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Impressed

I'm not too sure I would feel up to the job myself. I haven't the slightest idea where one would get the basic knowledge of teardown and rebuild, not to mention the specialized tools needed for the job. Plus what about the special lubricant material itself? So with that in mind, I'm impressed that you were able to get it all back together again and working! More power to you.

QuoteOriginally posted by MattGunn Quote
As this lens is so short the helix for the focus mechanism will also be unusually short. In order to get the same level of damping as their other MF lenses, pentax may have used a different grease. It is quite possible that this will have aged differently from their normal grease and thickened making the focus stiffer.
If the focus is stiff but smothe then viscous grease may well be the cause and it should be possible to dismantle the lens, clean the old grease off and re-lubricate. I have cleaned an re-lubricated several lenses (usually because they were gritty and full of sand) and have not encountered any problems.
10-15-2009, 09:40 AM   #10
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QuoteOriginally posted by solar1 Quote
I'm not too sure I would feel up to the job myself.
If the lens is in good condition otherwise I understand that this is the man to trust for the repair job.
10-15-2009, 12:25 PM   #11
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QuoteOriginally posted by solar1 Quote
I'm not too sure I would feel up to the job myself. I haven't the slightest idea where one would get the basic knowledge of teardown and rebuild, not to mention the specialized tools needed for the job. Plus what about the special lubricant material itself? So with that in mind, I'm impressed that you were able to get it all back together again and working! More power to you.
It is actually a lot easyer than you would think. Tools required include a good set of small screwdrivers, an old rubber bung and a good pair of tweezers and of course reasonable eyesight. For most of the lenses I have re-lubricated I have used standard automotive grease.
The best way to learn is to get a few of old, damaged, cheep lenses (plenty on ebay) and have a go. If then lens was cheep then you don't lose much if it goes wrong, and provided you don't lose any bits you can try again and again untill it is right. The first couple of lenses took a few tries but I generally get everything cleaned up and working first time now. Have a go, it is a usefull skill, it can save you a lot of money and it is very satisfying when it all works. Just stay away from AF lenses to start with, they have far too many small moving parts.
10-17-2009, 07:10 AM   #12
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Thank you littlelaker for the link (I recall this one from some time back but lost the link) and MattGun for the encouragement, I just have to figure out what a rubber bung is over this side of the pond.
10-17-2009, 07:49 AM   #13
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QuoteOriginally posted by solar1 Quote
I just have to figure out what a rubber bung is over this side of the pond.
It is just the name for a large rubber cork used in a lab for sealing glasware. I found one that is just the right size for removing lens trim rings on most lenses. Alternatives are ruber ends for walking sticks etc but there are purpose designed tools such as the one here:
Micro-Tools Europe (English): Lens Ring Tool Set
10-17-2009, 12:25 PM   #14
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I have two of them ...both work just fine - no stiffness.
10-17-2009, 01:00 PM   #15
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I use one of these to get the front ring off my lenses.



Its a rubber pipe cap and they come in various diameters so you should be able to get one the matches the front ring of your lens. I got this one a store that sells rubber products but I imagine any big hardware store would sell them. From memory it was about $12. The thickness of the walls almost perfectly matches the front ring of my M50 f1.4. I had tried using a pencil eraser before but never really had much luck but with this it is very easy to remove he front ring.
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