Pentax-M 50/1.7 ridiculously easy to clean fungus

RussellInCincinnti · 12-22-2013, 09:34 AM

Noticed light fungus behind the rear element on a Pentax-M 50mm F/1.7 lens. It was about 90 seconds of work to remove the retaining ring on the rear element with a $25 dollar (new) retaining ring wrench, let the rear glass drop out, clean both sides of the glass with ordinary lens fluid and an old cotton rag, and reassemble. How nice that the mechanical construction of this lens is so straightforward.

stevebrot · 12-22-2013, 10:51 AM

Welcome to the Pentax Forums! Glad your lens cleaned up nicely. With any luck the fungus will not recur.

Steve

RussellInCincinnti · 12-22-2013, 11:30 AM

My new theory is that undisturbed/unused lenses (like my Pentax 50/1.7 that had not been touched in decades) suffer fungus accumulation much more than ones that are used regularly. Because the gases released by the fungal activity, that probably speed up future fungal activity, are not dissipated by air currents. Related to the way so many fruits ripen faster in a paper bag.

johnyates · 12-22-2013, 04:05 PM

Originally posted by RussellInCincinnti

a $25 dollar (new) retaining ring wrench

Where did you get the wrench?

stevebrot · 12-22-2013, 07:03 PM

Originally posted by johnyates

Where did you get the wrench?

micro-tools.com has them.

johnyates · 12-22-2013, 10:27 PM

Originally posted by stevebrot

micro-tools.com has them.

Thanks!

12-22-2013, 09:34 AM	#1
RussellInCincinnti New Member Join Date: Dec 2013 Posts: 2	Pentax-M 50/1.7 ridiculously easy to clean fungus Noticed light fungus behind the rear element on a Pentax-M 50mm F/1.7 lens. It was about 90 seconds of work to remove the retaining ring on the rear element with a $25 dollar (new) retaining ring wrench, let the rear glass drop out, clean both sides of the glass with ordinary lens fluid and an old cotton rag, and reassemble. How nice that the mechanical construction of this lens is so straightforward.

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12-22-2013, 10:51 AM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Welcome to the Pentax Forums! Glad your lens cleaned up nicely. With any luck the fungus will not recur. Steve

12-22-2013, 11:30 AM	#3
RussellInCincinnti New Member Join Date: Dec 2013 Posts: 2 Original Poster	My new theory is that undisturbed/unused lenses (like my Pentax 50/1.7 that had not been touched in decades) suffer fungus accumulation much more than ones that are used regularly. Because the gases released by the fungal activity, that probably speed up future fungal activity, are not dissipated by air currents. Related to the way so many fruits ripen faster in a paper bag.

12-22-2013, 04:05 PM	#4
johnyates Pentaxian Join Date: Aug 2011 Location: Saskatoon, SK Photos: Albums Posts: 1,345	Originally posted by RussellInCincinnti a $25 dollar (new) retaining ring wrench Where did you get the wrench?

12-22-2013, 07:03 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by johnyates Where did you get the wrench? micro-tools.com has them.

12-22-2013, 10:27 PM	#6
johnyates Pentaxian Join Date: Aug 2011 Location: Saskatoon, SK Photos: Albums Posts: 1,345	Originally posted by stevebrot micro-tools.com has them. Thanks!