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03-09-2011, 08:56 PM   #1
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Cleaning internal elements - SMC-M 50mm f1.7

I acquired a SMC-M 50mm f1.7 from a St. Vincent De Paul for $3, and I've been enjoying it quite a lot (I'll probably be buying primes instead of zooms from now on). However, it has a rainbow sheen on an internal element when viewed from an angle. I hadn't noticed anything showing up on my photos, so I dismissed it. However, I just noticed some blue splotches on an otherwise nice photo that I expect were caused by it.


The spots can be seen between the right two lamps. The sun is probably close to in-frame, as the second photo I took here shows bad lens flare.




And a blurry photo of the lens:



It seems that removing the front element shouldn't be too difficult, per the link below, given that I'm comfortable opening things up. However, I'm not sure what to clean the lens with. It looks to me like the problem is oil, not fungus, so I'm guessing that a detergent and a lens cloth would suffice, but I'd rather do this all in one go, so I'd appreciate thoughts about what I should have on hand to do the actual cleaning.

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/72755-repairing...m-1-1-7-a.html

03-09-2011, 10:56 PM   #2
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It looks like your lens was made in Taiwan - it doesn't say Japan on the name ring like this one. I don't think it matters except the Taiwan ones may have a plastic name ring. Plastic ones can be pried off in extreme cases and possibly survive; metal gets trashed.



Either way, the ring has to come off. Here's what you see when that happens. Remove the filter ring by removing the screws marked with red arrows.



You'll see this. You want to unscrew the front lens group by using the spanner slots marked with green arrows. You don't need to worry about the screws marked with red arrows; they attach the focus ring. The unmarked screws (also visible in cutouts in the previous photo) allow you to remove the entire lens tube and aperture. You don't need to do that either.



If you're successful, the lens looks like this:



The front group has three lens elements. If you're lucky, simply cleaning the now-accessible rear surface will be fine. The frontmost element has a ring with spanner slots inside the ones you just used. That can be removed to lift the element out and access more surfaces. Note its curvature - I usually mark the front with a fingerprint. The rear element is held on with a ring which is sometimes glued. Check for adhesive before getting out the hacksaw. Lacquer thinner might work on the glue.

For cleaning, Windex probably will work.
03-10-2011, 04:34 AM   #3
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Dave,

Great information as usual. Thanks for sharing. Would the A version be similar?

Thanks,
03-10-2011, 04:50 AM   #4
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I've just started this new adventure as well in cleaning old lenses. I started a thread here:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/135750-basic-l...aning-kit.html

Fantastic amount of information on what you will need to get these things opened. I just started putting together a kit of tools, cleaning agents & most of all the information of those who've been doing this stuff for years. I would love to hear how it works out for you as well.

Thanks Dave for the pictures of the lenses and how to remove it. I need that visual big time..

04-02-2011, 11:53 AM   #5
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I just wanted to say thanks. My first pass at this, I got stuck after removing the front group. Another user in another post suggested using scissors as calipers, which worked fine for my purposes, and allowed me to open up the front group. After that, it was just a matter of disassembly.

04-02-2011, 08:35 PM   #6
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QuoteOriginally posted by alphanerd Quote
I just wanted to say thanks. My first pass at this, I got stuck after removing the front group. Another user in another post suggested using scissors as calipers, which worked fine for my purposes, and allowed me to open up the front group. After that, it was just a matter of disassembly.
Excellent. And thanks for the picture. It really helps to see what is there & where it goes. How did the cleaning go and are you happy with the results?
04-03-2011, 02:24 PM   #7
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Well met!

I'm in the process of cleaning a prime as well (50mm 1.7 Asahi) it was/is in good condition but dusty and with a bit of sand inside the focusing ring.

My question is, what lubrifiant should i use inside for the focusing ring? For the moment i used oil for precise mechanisms (not sure what the English terminology is for this kind of product, it's a verbatim translation of how it sounds in Romanian

This oil is basically finelly distilled petrolium fractions.

Is there another product better suited for this operation (not fine oil but maybe some vaseline?) The focusing ring, while not moving that bad isn't quite as smooth as it was. If you give me some hints please link the item somewhere where it's being sold, or the exact name of the product so i can identify it somehow. I have a friend that will be in the USA until 20th of april and i could have him bring this item if needed.

Much appreciated!
04-03-2011, 04:28 PM   #8
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Oil and plastic == not good. Vaseline= petrol based, not safe for plastic.

Silicone + plastic or metal == okay.

Now as for how that applies to lenses, you should wait for someone more knowing my opinions are based on home repair experience.

04-03-2011, 05:25 PM   #9
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QuoteOriginally posted by Penumbra Quote
Well met!

I'm in the process of cleaning a prime as well (50mm 1.7 Asahi) it was/is in good condition but dusty and with a bit of sand inside the focusing ring.

My question is, what lubrifiant should i use inside for the focusing ring? For the moment i used oil for precise mechanisms (not sure what the English terminology is for this kind of product, it's a verbatim translation of how it sounds in Romanian

This oil is basically finelly distilled petrolium fractions.

Is there another product better suited for this operation (not fine oil but maybe some vaseline?) The focusing ring, while not moving that bad isn't quite as smooth as it was. If you give me some hints please link the item somewhere where it's being sold, or the exact name of the product so i can identify it somehow. I have a friend that will be in the USA until 20th of april and i could have him bring this item if needed.

Much appreciated!

You can order it online here. www.Micro-Tools.com

It's called, Helical Focusing Grease.
Here the product info:HG-10 Helical #10 (Light) 8ml.

The cost is a little high at $24.95US. However, it's what is used on the Helical Focusing Ring.

There are some others as well, but I went with what is the best to use on them.
04-03-2011, 05:31 PM   #10
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I'm going to go out on a limb here and offer some generalities that have worked well for me over the years. I've divided lubricant applications into a few functional categories:

Slow moving parts (things you move with your finger like film advance parts and aperture rings) -- a light grease often recommended for firearms and fishing tackle. Less 'sticky' than Vasoline but does not flow or noticeably thin under the heat of a light bulb or get hard in cold weather..

Fast moving parts (things that 'snap' under spring pressure like shutter drive parts, but not aperture blades) -- A very light household oil like 3-in-1, watchmakers oils, sewing machine oil and rarely, powdered graphite slurry mixed with lighter fluid.

High friction parts (like latch engagements and gear teeth under spring pressure) -- Molybdenum paste.

Aperture blades (things not under pressure but which have 'drag' against adjacent surfaces) -- NO grease or oil! Dry graphite applied by brush or in a lighter fluid slurry. If you can see grain in the graphite it's too course. Might be applied directly to the blades using the tip of a very soft lead pencil or rub the pencil lead against a matchbook striker strip. Gently wipe/blow out as much excess as possible after operating the parts to spread the graphite.

Helical focus and zoom threads (a viscous automotive gear or bearing grease) -- ideally you'll have some old threaded barrels to experiment with to get the correct "feel"; it mostly depends on the tolerance in the threads. Something about like extra thick Vasoline usually works OK. (Peanut butter's too thick and honey's too 'sticky' unless you have a zoom that acts like a trombone slide when you tip it down. )

Plastic parts of any kind (you know, THOSE lenses) -- Caution! organic bases and solvents may affect plastics in undesirable ways, read instructions and experiment on junk parts. Plastic-to-plastic is the one area I can recommend silicon-based lubes but light grease is still better IMO.

If a lubricant smells or feels like it might give off volatile vapors of any kind as to solvent carrier evaporates, or under high temperatures, you can expect that it will probably deposit haze on lens elements over time.

Grease that turns 'runny' under the heat of a light bulb will surely migrate to places you don't want it to when exposed to summertime temperatures.

In my experience, WD-40 and similar pressurized fluids are NOT an answer to any camera lubrication problem unless used solely as a penetrating fluid for disassembling corroded parts to be cleaned later.

If you're uncertain as to what's available to you locally, a jeweler/watch/camera repairman, a machinist or a modeller may offer excellent advise regarding easily available products - although you might discuss the above categories with them to ensure they understand your intended application.

A little research on "lubricant-related" search strings including automotive, firearms, fishing tackle, lathes & machining metals, sewing machines, and cameras will be well rewarded. As usual, every ol' f@rt will have a conflicting opinion as to what's best.

H2

I'll push this over to the Articles > Maintenance Section as well. I most certainly invite others to contribute their experience and opinion to that topic as I have only past personal success to rely on here.

https://www.pentaxforums.com/forums/maintenance-repair-articles/139172-lubric...ml#post1452966

Last edited by pacerr; 04-03-2011 at 05:51 PM.
04-03-2011, 08:30 PM   #11
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QuoteOriginally posted by pacerr Quote
I'm going to go out on a limb here and offer some generalities that have worked well for me over the years. I've divided lubricant applications into a few functional categories:

Slow moving parts (things you move with your finger like film advance parts and aperture rings) -- a light grease often recommended for firearms and fishing tackle. Less 'sticky' than Vasoline but does not flow or noticeably thin under the heat of a light bulb or get hard in cold weather..

Fast moving parts (things that 'snap' under spring pressure like shutter drive parts, but not aperture blades) -- A very light household oil like 3-in-1, watchmakers oils, sewing machine oil and rarely, powdered graphite slurry mixed with lighter fluid.

High friction parts (like latch engagements and gear teeth under spring pressure) -- Molybdenum paste.

Aperture blades (things not under pressure but which have 'drag' against adjacent surfaces) -- NO grease or oil! Dry graphite applied by brush or in a lighter fluid slurry. If you can see grain in the graphite it's too course. Might be applied directly to the blades using the tip of a very soft lead pencil or rub the pencil lead against a matchbook striker strip. Gently wipe/blow out as much excess as possible after operating the parts to spread the graphite.

Helical focus and zoom threads (a viscous automotive gear or bearing grease) -- ideally you'll have some old threaded barrels to experiment with to get the correct "feel"; it mostly depends on the tolerance in the threads. Something about like extra thick Vasoline usually works OK. (Peanut butter's too thick and honey's too 'sticky' unless you have a zoom that acts like a trombone slide when you tip it down. )

Plastic parts of any kind (you know, THOSE lenses) -- Caution! organic bases and solvents may affect plastics in undesirable ways, read instructions and experiment on junk parts. Plastic-to-plastic is the one area I can recommend silicon-based lubes but light grease is still better IMO.

If a lubricant smells or feels like it might give off volatile vapors of any kind as to solvent carrier evaporates, or under high temperatures, you can expect that it will probably deposit haze on lens elements over time.

Grease that turns 'runny' under the heat of a light bulb will surely migrate to places you don't want it to when exposed to summertime temperatures.

In my experience, WD-40 and similar pressurized fluids are NOT an answer to any camera lubrication problem unless used solely as a penetrating fluid for disassembling corroded parts to be cleaned later.

If you're uncertain as to what's available to you locally, a jeweler/watch/camera repairman, a machinist or a modeller may offer excellent advise regarding easily available products - although you might discuss the above categories with them to ensure they understand your intended application.

A little research on "lubricant-related" search strings including automotive, firearms, fishing tackle, lathes & machining metals, sewing machines, and cameras will be well rewarded. As usual, every ol' f@rt will have a conflicting opinion as to what's best.

H2

I'll push this over to the Articles > Maintenance Section as well. I most certainly invite others to contribute their experience and opinion to that topic as I have only past personal success to rely on here.

https://www.pentaxforums.com/forums/maintenance-repair-articles/139172-lubric...ml#post1452966
Excellent. I'm still putting my kit together and glad to see what works.
04-04-2011, 12:56 AM   #12
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Huge help!

Thank you, gentlemen!
06-26-2013, 02:33 PM   #13
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This thread helped me clean a rather large dust spec from the back of the front group. Easy clean once I got to it. Awesome!!
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