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06-16-2021, 02:13 AM   #1
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New Acquisitions: Pentax S1a & Pentax ME!

Just thought I would share some news (that's exciting for me) and solicit some advice.

I'm based in England, and I've been scouring the 'e-Bay' for good deals on Pentax 35mm equipment over the past several months. I put in two offers over the past couple of weeks expecting only 1 to come through, but they both did (thereby testing my wallet).

I acquired a circa-1962 Pentax S1a body that came with three lenses—a Soligor 135mm, a Hanumar 28mm and the typical Super-Takumar 55mm f2. After getting the camera home, I've determined that the shutter only seems to be firing at one speed no matter where the position of the dial is, but I have very little background in camera repair and I haven't pursued a fix just yet.

My questions about this little S1a bundle for the forum are:
  • How dangerous is the radioactivity of the Super-Takumar 55mm f2 lens with Thorium lens coatings? Should I keep it and use it, or sell it off?
    • I have a newborn at home, and we live in a 2-bedroom apartment, so at the moment, I have the lens hidden away in the closet.
    • I'm inclined to sell off this lens because of the potential health risks, but I also know that the lens has a great reputation.
  • Are there any simple repair procedures I could try to rejuvenate this S1a camera body myself, or would I be better off sending it to a professional technician?
    • I don't have heaps of expendable income at the moment, so I'm inclined to tinker a little bit myself.
    • In terms of repair skill, I have worked a bit on disassembling, cleaning and reassembling lenses over the past 6 months, and I feel confident in those abilities, but I haven't tinkered with SLR bodies yet.
I also acquired a circa-1982 Pentax ME body that also came with a flash unit (Pentax AF160), 5 Cokin A-series filters, and 3 lenses (a Sun 80-200mm, an 'Image by Vivitar' 28mm and the typical SMC Pentax-M 50mm f1.7). This bundle came with all the original boxes and manuals, and the lenses in particular seem as if they have never (or only very lightly) been used. The original receipt (dated 1983) for the camera was inside as well, showing that the £98 that the camera's original owner paid for the camera, flash and 50mm f1.7 are equivalent to about £340 in today's money ().


After receiving the ME in the post, I popped a couple of LR44 button cell batteries inside. Lo and behold, the internal light meter and automatic variable shutter speeds seem to work like a charm! I hope to shoot a roll or two of film on this bad boy during the next week or two to see how it all works out.

The only question I have about my Pentax ME bundle for this forum is:
  • Should I replace the light seals and foam mirror slap cushions in the camera before beginning to use it regularly?
    • Similar to my questions above, do you all think that I should attempt this maintenance myself? Or would it be better (given that the camera is currently in perfect working order) to leave this basic maintenance to a professional?
Thanks for taking the time to read my post, and I look forward to any commiserations, congratulations or advice that anyone's willing to provide!

06-16-2021, 04:00 AM   #2
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As regards the radioactive lens, just stop worrying, the amount of radiation they emit is about the same as the normal background radiation that we are all exposed to. In fact you would get a higher dose of radiation by visiting Cornwall where there the granite bedrock emits a high amount of radiation.

I would suggest that the foam seals and the mirror bumpers in particular will need replacing in both cameras to get any sort of reliable operation.

As regards the S1a shutter, it sounds like it is suffering with dried up grease problems which can involve a lot of work to rectify and I wouldn't recommend that you try yourself if haven't had any experience of shutter repair, definitely do not start oiling things because you will only cause other problems. Either get it repaired professionally or just keep it as a non-working start of your collection ( it sounds like you are going to have a collection eventually ).
06-16-2021, 04:53 AM   #3
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QuoteOriginally posted by archaeodude Quote
How dangerous is the radioactivity of the Super-Takumar 55mm f2 lens with Thorium lens coatings? Should I keep it and use it, or sell it off?
Here are some links you might find useful or at least maybe interesting:


Radioactive Pentax Takumar lenses.

How much radiation is too much? A handy guide

Radioactive lenses | Camerapedia | Fandom

A Look at the Radioactivity of Old Manual Lenses | PetaPixel

A Radioactive Lens

Radioactive lenses


A couple years ago I was thinking about purchasing some of the old Takumar radioactive lenses. It seems the total exposure from thoriated lenses in normal use is very low. But after giving the matter a lot of thought, I decided to avoid radioactive lenses just for my own peace of mind.
06-16-2021, 07:07 PM   #4
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Nice equipment acquisition.

Unless you are sleeping with the lens you probably absorb more background radiation outdoors or from your cell phone then you would from using the lens the same amount of time.

06-17-2021, 02:51 AM   #5
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Usually the light seals and the mirror foam of a ME Super are allready sticky, if they have not been replaced allready. Simply poke the seals with your finger and if you get the slightest damp or sticky feeling those foams have to be replaced. Do not use a camera with sticky seals or mirror foam. Especially the mirror foam will surely come of and soil the inside of the camera. Getting the camera cleaned afterwards is really tricky. The light seals might get into the shutter or soil your film. So, when you have dissolving foam in an old camera do yourself a favour and replace it before using. An easy task for the ME.
06-17-2021, 06:17 AM   #6
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QuoteOriginally posted by archaeodude Quote
Just thought I would share some news (that's exciting for me) and solicit some advice.

I'm based in England, and I've been scouring the 'e-Bay' for good deals on Pentax 35mm equipment over the past several months. I put in two offers over the past couple of weeks expecting only 1 to come through, but they both did (thereby testing my wallet).

I acquired a circa-1962 Pentax S1a body that came with three lenses—a Soligor 135mm, a Hanumar 28mm and the typical Super-Takumar 55mm f2. After getting the camera home, I've determined that the shutter only seems to be firing at one speed no matter where the position of the dial is, but I have very little background in camera repair and I haven't pursued a fix just yet.

My questions about this little S1a bundle for the forum are:
  • How dangerous is the radioactivity of the Super-Takumar 55mm f2 lens with Thorium lens coatings? Should I keep it and use it, or sell it off?
    • I have a newborn at home, and we live in a 2-bedroom apartment, so at the moment, I have the lens hidden away in the closet.
    • I'm inclined to sell off this lens because of the potential health risks, but I also know that the lens has a great reputation.
  • Are there any simple repair procedures I could try to rejuvenate this S1a camera body myself, or would I be better off sending it to a professional technician?
    • I don't have heaps of expendable income at the moment, so I'm inclined to tinker a little bit myself.
    • In terms of repair skill, I have worked a bit on disassembling, cleaning and reassembling lenses over the past 6 months, and I feel confident in those abilities, but I haven't tinkered with SLR bodies yet.
I also acquired a circa-1982 Pentax ME body that also came with a flash unit (Pentax AF160), 5 Cokin A-series filters, and 3 lenses (a Sun 80-200mm, an 'Image by Vivitar' 28mm and the typical SMC Pentax-M 50mm f1.7). This bundle came with all the original boxes and manuals, and the lenses in particular seem as if they have never (or only very lightly) been used. The original receipt (dated 1983) for the camera was inside as well, showing that the £98 that the camera's original owner paid for the camera, flash and 50mm f1.7 are equivalent to about £340 in today's money ().


After receiving the ME in the post, I popped a couple of LR44 button cell batteries inside. Lo and behold, the internal light meter and automatic variable shutter speeds seem to work like a charm! I hope to shoot a roll or two of film on this bad boy during the next week or two to see how it all works out.

The only question I have about my Pentax ME bundle for this forum is:
  • Should I replace the light seals and foam mirror slap cushions in the camera before beginning to use it regularly?
    • Similar to my questions above, do you all think that I should attempt this maintenance myself? Or would it be better (given that the camera is currently in perfect working order) to leave this basic maintenance to a professional?
Thanks for taking the time to read my post, and I look forward to any commiserations, congratulations or advice that anyone's willing to provide!
I have replaced dozens of seals myself. Find some adhesive backed felt, or thin sheet foam, and cut strips. Use a toothpick to clean out the old powdery or gummy foam from the grooves. Same with the mirror stop. Isopropyl alcohol or methes can help here. Make sure to protect the inside of the camera from debris falling in.
About the sound of the S1A shutter; put the speed to 1 second, then open the back and see if the shutter is open for that time. You can't go on sound because "speed" is done with the gap between the two curtains which travel at a constant speed. You can undo the 4 screws on the bottom and use a toothpick to drop some very light oil on cogs, That has freed up many a sluggish shutter.
06-17-2021, 03:31 PM   #7
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Only replace the seals and mirror foam if it needs it! I bought an ME a while ago and it was perfect.
These are very nice cameras.

You can post pics of the mirror foam etc if you are not sure.

06-18-2021, 06:45 AM   #8
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QuoteOriginally posted by Ray-uk Quote
As regards the radioactive lens, just stop worrying, the amount of radiation they emit is about the same as the normal background radiation that we are all exposed to. In fact you would get a higher dose of radiation by visiting Cornwall where there the granite bedrock emits a high amount of radiation...
QuoteOriginally posted by eles Quote
Here are some links you might find useful or at least maybe interesting:


Radioactive Pentax Takumar lenses.

How much radiation is too much? A handy guide

Radioactive lenses | Camerapedia | Fandom

A Look at the Radioactivity of Old Manual Lenses | PetaPixel

A Radioactive Lens

Radioactive lenses


A couple years ago I was thinking about purchasing some of the old Takumar radioactive lenses. It seems the total exposure from thoriated lenses in normal use is very low. But after giving the matter a lot of thought, I decided to avoid radioactive lenses just for my own peace of mind.
QuoteOriginally posted by Not a Number Quote
Nice equipment acquisition.

Unless you are sleeping with the lens you probably absorb more background radiation outdoors or from your cell phone then you would from using the lens the same amount of time.
Thank you all for sharing these words of wisdom and encouragement. The internet links about radioactive lenses were certainly useful, and I feel like I have a bit more knowledge on the subject.

I do live in a university town, so I am hoping to track down a curious student (or faculty member) who may be willing to help me test my lens (and perhaps additional equipment) for radioactivity. Of course if I am successful in my quest, I will share the information I find here on the forums!

Thanks again!

---------- Post added 06-18-21 at 06:47 AM ----------

QuoteOriginally posted by Ray-uk Quote
As regards the radioactive lens, just stop worrying, the amount of radiation they emit is about the same as the normal background radiation that we are all exposed to. In fact you would get a higher dose of radiation by visiting Cornwall where there the granite bedrock emits a high amount of radiation.

I would suggest that the foam seals and the mirror bumpers in particular will need replacing in both cameras to get any sort of reliable operation.

As regards the S1a shutter, it sounds like it is suffering with dried up grease problems which can involve a lot of work to rectify and I wouldn't recommend that you try yourself if haven't had any experience of shutter repair, definitely do not start oiling things because you will only cause other problems. Either get it repaired professionally or just keep it as a non-working start of your collection ( it sounds like you are going to have a collection eventually ).
QuoteOriginally posted by Papa_Joe Quote
Usually the light seals and the mirror foam of a ME Super are allready sticky, if they have not been replaced allready. Simply poke the seals with your finger and if you get the slightest damp or sticky feeling those foams have to be replaced. Do not use a camera with sticky seals or mirror foam. Especially the mirror foam will surely come of and soil the inside of the camera. Getting the camera cleaned afterwards is really tricky. The light seals might get into the shutter or soil your film. So, when you have dissolving foam in an old camera do yourself a favour and replace it before using. An easy task for the ME.
QuoteOriginally posted by arnold Quote
I have replaced dozens of seals myself. Find some adhesive backed felt, or thin sheet foam, and cut strips. Use a toothpick to clean out the old powdery or gummy foam from the grooves. Same with the mirror stop. Isopropyl alcohol or methes can help here. Make sure to protect the inside of the camera from debris falling in.
About the sound of the S1A shutter; put the speed to 1 second, then open the back and see if the shutter is open for that time. You can't go on sound because "speed" is done with the gap between the two curtains which travel at a constant speed. You can undo the 4 screws on the bottom and use a toothpick to drop some very light oil on cogs, That has freed up many a sluggish shutter.
QuoteOriginally posted by Huss Quote
Only replace the seals and mirror foam if it needs it! I bought an ME a while ago and it was perfect.
These are very nice cameras.

You can post pics of the mirror foam etc if you are not sure.
I very much appreciate all of this information and suggestions!

It sounds like the light seals (if necessary upon further reflection) might be a repair that my novice hands could realistically undertake.

I may reconsider trying to work on the S1a myself, but I have noticed here on PentaxForums that our very own ismaelg started a wonderful S1a repair thread about 9 months ago. If I do end up doing any repairs, then I may attempt to document them for the forum!

Many thanks!
06-18-2021, 02:41 PM   #9
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Seals aren't difficult to replace, just tedious. It can take a while to clean out the sticky gunk left by the old ones.
06-23-2021, 12:13 PM   #10
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QuoteOriginally posted by womble Quote
Seals aren't difficult to replace, just tedious. It can take a while to clean out the sticky gunk left by the old ones.
Thanks for the words of encouragement!

I haven't posted an update just yet because my wife gave birth to our first child over the weekend. I suppose that I may be hard-pressed to begin my Pentax S1a and Pentax ME work for a few weeks ... or months ... or years ...


If and when I do begin my repair journey, I'll be sure to post my experience and findings here for all to benefit!
08-19-2021, 05:12 AM - 2 Likes   #11
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QuoteOriginally posted by eles Quote
Here are some links you might find useful or at least maybe interesting:


Radioactive Pentax Takumar lenses.

How much radiation is too much? A handy guide

Radioactive lenses | Camerapedia | Fandom

A Look at the Radioactivity of Old Manual Lenses | PetaPixel

A Radioactive Lens

Radioactive lenses


A couple years ago I was thinking about purchasing some of the old Takumar radioactive lenses. It seems the total exposure from thoriated lenses in normal use is very low. But after giving the matter a lot of thought, I decided to avoid radioactive lenses just for my own peace of mind.
Well, I've been able to get conclusive confirmation about the levels of radioactivity associated with my Super Takumar 55mm f/2. I contacted a Radiation Safety Officer at a local university, and much to my surprise, he agreed to undertake a few tests on my camera equipment. It turned out that my 55mm f/2 was not emitting any measurable radiation.

On the other hand, a 55mm f/1.8 that I recently acquired was measured to emit approximately 2 microSieverts per hour (gamma and beta radiation). This radiation was coming from the lens's rear element. I was told that the typical yearly radiation exposure associated with living where I live is approximately 2 milliSieverts per year, and that an exposure dose of approximately 10 milliSieverts per year is deemed to not be too awfully dangerous for members of the general public.

The measurable radiation declined substantially (to approximately 0.5 microSieverts per hour) when measurements were taken at the back of my Pentax S1a when the 'hot' lens was mounted to the camera. Additionally, a measurement of the unmounted rear element of the lens at a range of 10cm showed a similar dose of approximately 0.5 microSieverts. Increasing the measurement distance to 1m showed no discernible difference as compared to the background radiation being detected in the office where we were standing.


In sum, the Radiation Safety Officer with whom I spoke explained that I would need to hold the rear element directly against my body for about 1,000 hours in order to achieve a level of exposure equivalent to what everyone experiences in the area where I live on a yearly basis. This works out to about 2 hours and 45 minutes every day for 1 year. If mounted on a camera, it would take approximately 4 times as long (i.e. 4,000 hours / almost 11 hours per day for a year) to reach the typical level of exposure in my lived environment.

All of this information has helped me to feel more comfortable keeping (and using) my radioactive lens.

I hope that this information proves of interest to others!
08-19-2021, 10:24 AM   #12
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from everything I have read the 55mm f1.8 and f2 are only mildly radioactive. The 50mm f1.4 is more of a concern.
08-20-2021, 04:57 PM   #13
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Wait. New baby at home and you haven't thrown a roll of film in the ME and made some baby pictures?
You need to get on that

I'd suggest Ilford XP2 so you can get it developed conveniently.
Some of my favorite baby photos are the B&W ones...

And congratulations!

-Eric
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