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12-05-2019, 08:33 PM   #1
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6x7 fungus

I have a functional copy of the 165mm for 6x7 systems that's got minor fungus in-between the final lens elements - it does not appear to come affect the final photos and if you are just glancing at the lens you'd miss it. It's not in the center of the element, the center 1/3 has been spared and the lens seems sharp when pixel peeping.

Should I be concerned how this will impact image quality? I've tried separating the rear elements group to clean (I have all the appropriate tools) but I could not get the last part of the assembly unscrewed (Maybe glued). If I've missed an easy way to fix please let me know. I really love the focal length and fast aperture so would love to feel confident in the IQ I can consistently expect.

Thanks for any assistance.

12-06-2019, 12:18 PM - 1 Like   #2
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There are plenty of videos showing the amount of abuse and dirt on the lenses in order to make any visible impact on the IQ of a picture.
Generally, the closer the dirt/fungus is to the rear of the lens, it is more likely to be visible, but still, it takes a lot to be seen in the image.

There is no simple quick fix to get rid of fungus on your lens surfaces, the only way is to disassemble and clean it carefully.
There are several "how to do" videos on YouTube, I'm not sure if there is one specific for your lens.
The 105mm shouldn't be too different though.

Try this for cleaning: clean fungus camera lens - YouTube
12-06-2019, 03:10 PM   #3
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QuoteOriginally posted by MrKodak Quote
There are plenty of videos showing the amount of abuse and dirt on the lenses in order to make any visible impact on the IQ of a picture.
Generally, the closer the dirt/fungus is to the rear of the lens, it is more likely to be visible, but still, it takes a lot to be seen in the image.

There is no simple quick fix to get rid of fungus on your lens surfaces, the only way is to disassemble and clean it carefully.
There are several "how to do" videos on YouTube, I'm not sure if there is one specific for your lens.
The 105mm shouldn't be too different though. Pentax 67 105mm 2.4 - Part 1 Disassembly - YouTube

Try this for cleaning: clean fungus camera lens - YouTube
Thank you for the share and vote of confidence for the lens condition. I haven't been able to find a video for the 165mm, unfortunately for this video he left out the step to address the rear most group.
12-09-2019, 04:14 PM   #4
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A small amount of fungus is not a concern. I would however suggest storing the lens in an area where the air is very dry. Fungus will grow in a humid environment and you sure don't want it spreading.

12-09-2019, 07:49 PM - 1 Like   #5
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I would also blast it with ultraviolet to kill the fungus.

All lens faults either degrade the image unacceptably or they don’t. If pixel peeping and the overall image quality pleases you, then use the lens and enjoy it.

As with any flaw, make sure it is shaded. Off-axis light exposes flaws.

Rick “judging lenses by the images they make” Denney
12-11-2019, 02:07 AM - 1 Like   #6
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I second the comment on ultra-violet. There are several ways to use UV on lenses, including some dedicated tools, and it is worth using one, if you have a lot of lenses, and specially old ones, and live in a humid area.
12-11-2019, 11:16 PM   #7
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UV light will not kill fungus, active or dormant; as a popular urban myth, it is no surprise it gets so much mention. Zeiss pioneered the treatment and removal of fungus, but does not offer this service to the public. Hydrogen peroxide drench and, where etching is evident, resurfacing and polishing. In short, if its an internal element, it is probably cheaper to buy a new lens and let nature take over the one with fungus.

There is a very good chance the lens has migrated fungus to other items it was stored next to. Humidity e.g. the tropics, is what gives the fungus its life and motility.
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