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05-01-2015, 03:41 PM - 1 Like   #16
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QuoteOriginally posted by Cuthbert Quote
Pretty sure all lenses have seals to protect the inner components from dust and especially to contain the oil in the blade mechanism and the grease of the focusing thread from spilling on the elements or outside. When we have oil on blades it means these seals started to leak.
Most vintage SLR lenses are sort of water resistant as an accident of design. The focus helicoid is full of grease and the other rings and such overlap in such a way to shed incidental splash. Add a filter and most are good to go in mist or spray. I don't know that I remember any lens other than modern ones and waterproof Nikonos Nikkors that have actual seals.

As for the oily blades...usually that is the result of the migration of the oil fraction of grease lubricants from the aperture mechanism over time onto the blades themselves. Another cause is poorly done service. The focus grease pretty much stays put.


Steve

05-01-2015, 07:21 PM   #17
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No, you can't. Steve is right. From personal experience servicing lenses, I can tell you that there are no seals such as the type you claim there to be in vintage Pentax lenses (or 99% of those from other brands).

The reason that dust/ minor splashes/etc tend not to get in them all that easily is that they tend to settle on the top of the lens and fall/flow off the sides, in addition to the very minor protection that the helical grease fives. When the lens does get hit by more substantial amounts of water, it will go right in. There are plenty of vintage lenses just like the K prime in that cutaway photo that have the steel aperture blades rusted together because water got into the lens.

And yes, oily blades are almost always caused by the liquification due to heat or poor formulation of helical grease, outside of the small number of older presets (none by Pentax) that have intentionally oiled blades.

QuoteOriginally posted by Cuthbert Quote
LX cutaway:



You can see all the lip seals in the lens.

Still, shooting in the rain with a 30 years old camera and lens is hazardous unless both have been freshly CLAd.
05-01-2015, 08:14 PM   #18
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QuoteOriginally posted by dcshooter Quote
And yes, oily blades are almost always caused by the liquification due to heat or poor formulation of helical grease
My mistake...
05-01-2015, 08:25 PM   #19
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Mistake? I thought I was agreeing with you!

Incidentally, I find the Pentax greases to be among the more stable greases among those made in the 60's-80's. Worst are Chinon and Komine-made Vivitars. I've had copies of the Series 1 28-90mm lens that have been mailed out with perfectly clean blades and have arrived completely seized up, presumably due to vibration or heat causing the grease to liquify/separate and migrate to the blades.

In some models, the migrated grease re-solidifies, either through the evaporation of the liquid fraction or re-solidification as temperatures fall, while in others, it stays liquid, giving the blades the classic "sluggish" symptoms.


QuoteOriginally posted by stevebrot Quote
My mistake...


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