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11-28-2020, 08:30 AM - 1 Like   #1
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Takumar lens cap *magic*. What gives?

You know how some folks have an addition to popping plastic wrap bubbles? I think I'm getting something akin to that with metal Takumar lens caps. Pulling them on and off, twisting the caps, there is a feeling that I can't really equate to anything else other than to say maybe cushioned luxury. While it is metal on metal they feel like there is a cushion of air adhesion between lens and cap. I can't say I've noticed this affect anywhere else.

So what is that feeling? Is there a vacuum created when you push the lens on? Is it some sort of electrostatic effect? Heck I'll even entertain the possibility that van der waals forces are in effect because Asahi fitted these lens/cap spects down to a molecular level.

Yes, this is a bit tongue-in-cheek, but I really am amazed that something as mundane as a lens cap can be manufactured to produce this effect. So someone who has some engineering knowledge or even just some gifted insider knowledge, I appreciate a little insight into what is going on with the mating of these two products.

11-28-2020, 08:46 AM - 2 Likes   #2
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I know what you mean. I have had Pentax cameras and lenses since '68. I have a few old Takumar lenses from that time period and I had an extra lens cap for a 49mm lens. Couple of years ago my wife bought me a new Ricoh GR ll, I also got the lens hood and adaptor accessory from Ricoh.

I put the adaptor on the little GR body and also screwed on a B & W 49mm glass filter onto to the adaptor....but Ricoh doesn't supply a lens cap. So I thought, I wonder if my 55 year old metal Takumar metal cap, with it's felt liner around the inner ring of the cap would work. Sure does and it looks real good having that Asahi Pentax name on the outside of the vintage cap on a modern camera.

The feeling you get is the very close tolerance of the cap fit and also the felt liner provides that luxurious vacuum and quality feel when you put on and take off the cap. You'd think it was crafted by Rolls-Royce...because of the quality, the look and the ergonomic feel of that cap.
11-28-2020, 08:51 AM - 3 Likes   #3
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It's because they're made of beskar...
11-28-2020, 08:53 AM - 1 Like   #4
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QuoteOriginally posted by stemked Quote
So what is that feeling? Is there a vacuum created when you push the lens on?
Actually, it would not be a vacuum, but increased air pressure. I have even noticed this with plastic lens caps. The only way to get push on caps to stay on it to make certain the tolerances between the lens and the cap are real tight. Yes, they did an exceptional job with this, and if you move a 49mm cap from one lens to another, the tolerances stay tight!
As you push the cap onto the lens, the air cannot escape quick, so you are compressing the air in the lens cavity, enough to feel a resistance. It does not take much to feel this, but it also points to the protection from the elements (moisture) the lens is also receiving from such lens caps. You may also notice that the cap is a bit hard to take off, this is vacuum, again, making it easier to keep the cap ON. Actually an elegant design!

11-28-2020, 09:16 AM   #5
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I don't own any Taks, but the cap on the 77 Ltd does give a similar sensation. I keep putting it on and off

---------- Post added 11-28-20 at 09:17 AM ----------

QuoteOriginally posted by boriscleto Quote
It's because they're made of beskar...
This is the (Pentax) Way.
So *that* is why our stuff is so sturdy
11-28-2020, 09:30 AM - 3 Likes   #6
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QuoteOriginally posted by Serkevan Quote
This is the (Pentax) Way.:
11-28-2020, 09:51 AM - 1 Like   #7
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QuoteOriginally posted by lesmore49 Quote
I know what you mean. I have had Pentax cameras and lenses since '68. I have a few old Takumar lenses from that time period and I had an extra lens cap for a 49mm lens. Couple of years ago my wife bought me a new Ricoh GR ll, I also got the lens hood and adaptor accessory from Ricoh.

I put the adaptor on the little GR body and also screwed on a B & W 49mm glass filter onto to the adaptor....but Ricoh doesn't supply a lens cap. So I thought, I wonder if my 55 year old metal Takumar metal cap, with it's felt liner around the inner ring of the cap would work. Sure does and it looks real good having that Asahi Pentax name on the outside of the vintage cap on a modern camera.

The feeling you get is the very close tolerance of the cap fit and also the felt liner provides that luxurious vacuum and quality feel when you put on and take off the cap. You'd think it was crafted by Rolls-Royce...because of the quality, the look and the ergonomic feel of that cap.
I have only a couple of Takumars with the original felt-lined metal cap. They are indeed lovely to fit and remove. I'll say, though, the push-on caps of certain HD DA Limiteds (and, I assume, their SMC ancestors) - specifically the 21, 35, 70 and 20-40 - arguably feel nicer still. They have a similar feeling of smooth pressure resistance when removing them, but - since they're machined (or cast?) - they're so solid in the hand. The DA20-40's cap, being larger, feels the nicest of all

11-28-2020, 11:00 AM   #8
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QuoteOriginally posted by BigDave Quote
Actually, it would not be a vacuum, but increased air pressure. I have even noticed this with plastic lens caps. The only way to get push on caps to stay on it to make certain the tolerances between the lens and the cap are real tight. Yes, they did an exceptional job with this, and if you move a 49mm cap from one lens to another, the tolerances stay tight!
As you push the cap onto the lens, the air cannot escape quick, so you are compressing the air in the lens cavity, enough to feel a resistance. It does not take much to feel this, but it also points to the protection from the elements (moisture) the lens is also receiving from such lens caps. You may also notice that the cap is a bit hard to take off, this is vacuum, again, making it easier to keep the cap ON. Actually an elegant design!
Thank you for that very elegant and logical response!
11-28-2020, 11:01 AM - 1 Like   #9
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QuoteOriginally posted by BigMackCam Quote
I have only a couple of Takumars with the original felt-lined metal cap. They are indeed lovely to fit and remove. I'll say, though, the push-on caps of certain HD DA Limiteds (and, I assume, their SMC ancestors) - specifically the 21, 35, 70 and 20-40 - arguably feel nicer still. They have a similar feeling of smooth pressure resistance when removing them, but - since they're machined (or cast?) - they're so solid in the hand. The DA20-40's cap, being larger, feels the nicest of all
I have some Limiteds...and I know what you mean. Bit of a digression....my 40 Ltd. has that small screw in lens cap. First I didn't like it, but the more I used it, I realized what a lovely, little, quirky but quite useful cap, which when you think about it, all those descriptors fit the Pentax way in camera design also.

Then of course there is my Russian 500mm lens with it's cap which is also quite different. But this is a cap, indeed a lens..... that very few of us, including you and me...know about. Exclusive club, eh.
11-28-2020, 11:04 AM   #10
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I've got that very book, probably a different printing though. Still look through it. Bert Keppler was a great photographic writer and magazine editor (Pop/Modern Photography). Very knowledgeable and respected through the photography industry.
11-28-2020, 11:21 AM - 2 Likes   #11
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QuoteOriginally posted by lesmore49 Quote
Then of course there is my Russian 500mm lens with it's cap which is also quite different. But this is a cap, indeed a lens..... that very few of us, including you and me...know about. Exclusive club, eh.
Indeed so. One of the best lenses of its type, IMHO

Actually, that got me thinking... A few of my earlier L39 rangefinder Soviet lenses have lined push-on metal caps that have a similar feel to the Takumars. The lining isn't felt, but a strip of finely woven cloth - and usually needs replacing. I use thin, adhesive-backed black felt that I found at a local homewares and DIY store. It's also fantastic for lining metal lens hoods, mount adapters and occasionally lens internals (such as the annoyingly-reflective plate component inside the Jupiter-21M ), as it seems to completely absorb reflected light... but as a lining for push-on lens caps - including Takumars - it's perfect
11-28-2020, 12:06 PM   #12
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QuoteOriginally posted by BigMackCam Quote
Indeed so. One of the best lenses of its type, IMHO

Actually, that got me thinking... A few of my earlier L39 rangefinder Soviet lenses have lined push-on metal caps that have a similar feel to the Takumars. The lining isn't felt, but a strip of finely woven cloth - and usually needs replacing. I use thin, adhesive-backed black felt that I found at a local homewares and DIY store. It's also fantastic for lining metal lens hoods, mount adapters and occasionally lens internals (such as the annoyingly-reflective plate component inside the Jupiter-21M ), as it seems to completely absorb reflected light... but as a lining for push-on lens caps - including Takumars - it's perfect
Good to know for my Tak caps if they need relining. Thx for the info.
11-28-2020, 10:04 PM   #13
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Love the old Tak lens caps. Is it wrong that I shun the ones that say Honeywell on them?
11-29-2020, 04:21 AM   #14
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Minolta used metal press-on style caps on their lenses and have a similar feel to the Asahi Pentax caps. They used (as far as I've seen) a leather, felt or soft plastic ring/gasket. If the gasket compressed with age and use the cap could become loose enough to potentially fall off. Depending on the material some warm water is usually enough to get the material to swell and restore a good fit.
11-29-2020, 08:59 AM   #15
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QuoteOriginally posted by Lhorn Quote
Love the old Tak lens caps. Is it wrong that I shun the ones that say Honeywell on them?
Me Too!
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