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02-28-2013, 04:52 PM   #16
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QuoteOriginally posted by Quicksand Quote
The most dangerous lens I have is an old 500mm f/6.3 Vivitar long lens. It's solid metal and glass and could probably do some serious damage when wielded as a weapon.
RioRico always said long lenses were more useful for fending off bears than taking pictures...

03-01-2013, 12:07 AM   #17
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QuoteOriginally posted by kiwi_jono Quote
There are radioactive lens coating (like on the Super Tak 50 f1.4)
The coatings aren't radioactive, the glass itself is radioactive. Thorium oxide was used to raise the refractive index of the glass used in the Takumar 50mm f/1.4,Takumar 35mm f/2. The coatings gradually turn yellow as a consequence of the alpha particle emissions from the glass*, alpha particles aren't all that dangerous they can be stopped by a few millimetres of air, they are only dangerous if you inhale substances that emit them. Pentax isn't the only maker who used Thorium oxide there are some Leica lenses that had Thorium oxide glass in them, but the most prolific maker of "hot" radioactive lenses would have to be Kodak - some of these lenses are so intensely radioactive if you sit one on an unexposed polariod in the dark after an hour the polariod will be completely fogged.

*it is possible to reverse this by exposing the lens to intense ultraviolet light.
03-08-2013, 10:56 AM   #18
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Thank you all for your responses. One follow-up question that i think i know the answer to, but would like confirmation. All of the responses above refer to everything but M42 lenses. Are there any M42 lenses that, when mounted with the Pentax adapter could in any way damage the camera? Thanks.
03-08-2013, 11:03 AM   #19
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There are third party M42 lenses that won't mount, i.e. Mamiya/Sekor SX lenses and early Helios 44-3s. But I don't know of any that would damage a Pentax DSLR.

There is a problem M42 bellows units though. Once it is mounted on the camera the flash overhang prevents it from being unscrewed. You should always use a flanged adapter or an adapter with the spring clip removed when using a bellows...


Last edited by boriscleto; 03-08-2013 at 11:11 AM.
03-08-2013, 11:10 AM   #20
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Yashinon-DX 50/1.4 & 50/1.7 have protruding elements that might hit the mirror on some cams when focused at infinity (certainly any future full-frame it will). I thought they would be safe with the mirrorless K-01, but there is actually less space in there -- when I tried the 1.7 it banged into the inner brick where there is an empty space for the viewfinder in the DSLR models...
03-08-2013, 12:22 PM   #21
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Well, we could talk about non-Penatax M42 adapters which get stuck ... plus lack of infinity if it's a flanged one ... J
03-08-2013, 05:20 PM   #22
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QuoteOriginally posted by toukan Quote
Are there any M42 lenses that, when mounted with the Pentax adapter could in any way damage the camera?
No. As I have said above Alpha particles can be stopped by a few mm of air and present no danger to digital cameras.
03-08-2013, 07:41 PM   #23
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Many lenses can suck the life from your wallet in a matter of seconds and leave it an empty shell of its former self.

03-08-2013, 10:04 PM   #24
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I had a Sears 70-210 I found at a discount store. It mounted just fine a couple of times... and then got stuck on my ZX-L. It took a Tiger Saw to get it off. So to reiterate what others have said, you can't just cram any PK mount lens on.
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