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Old 28-08-2010, 08:07 AM
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How to clean haze in Canon 300mm nFD lens

I just acquired this lens on ebay .. and I want to dismantle it already
Has anyone tried this before?


OK, I found the way.. sorry for bothering you guys..
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Last edited by bojan; 02-09-2010 at 06:42 PM.
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Old 02-09-2010, 05:45 PM
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Bad news..
Dismantling went well, cleaning of fungus (with windex) was also successful..
But, the central meniscus is slightly milk-hazy at edges.. and it can't be washed away.
What could it be? It is not fungus..
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Old 12-09-2010, 09:48 AM
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Smile Haze is still there, but not affecting image quality

The slight haze, localised at the edges of the internal meniscus is still there (probably oxidised coating ? ), I could not get rid of it, so I decided to leave it as is for now.

However, this does not affect the image quality a lot... if any at all.
After re-assembling the whole thing together, here is the first result: Not bad for $100 lens, not bad at all .
I am happy with the whole exercise.

The composite picture, with crops (100% size) from corresponding parts of the frame is attached. It is a stack of 10x10 sec frames, no darks and no flats, with external f/5.6 aperture (because I removed all the un-necessary guts from the lens)

It is probably inferior to it's twin brother ("L" version), but it is definitely good enough for everything I intend to use it for in the future.

The adapter assembly and fogged internal lens pics are also attached.
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Last edited by bojan; 12-09-2010 at 03:31 PM.
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Old 29-01-2012, 02:11 PM
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300mm F4 internal element cleaned !

After stumbling on this website:
http://www.kyphoto.com/classics/foru...tml?1323826810, discussion with some members and careful reading of other posts, yesterday I tried with vinegar.
The "fog" is almost completely gone (it's visible where it was only if illuminated by direct sunlight).

When I started to brag about my results to my wife, she said "you should have asked me.. vinegar is the BEST cleaning agent of all, works on everything and it doesn't leave the scratches.."
Looks like fungus in lenses is not the problem any more..

Last edited by bojan; 29-01-2012 at 02:45 PM.
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Old 29-01-2012, 02:37 PM
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Some older exotic glasses can yellow/brown/haze that can be corrected by exposure to UV light.
http://www.youtube.com/watch?v=k6cPLBonMXA
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Old 29-01-2012, 03:39 PM
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Excellent work Bojan, and thanks for the info. I have a pair of old bino's that are hazy as, so I will attack them with vinegar!

Cheers,
Jason.
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Old 29-01-2012, 04:50 PM
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Good to hear you've got your lens back but fungus does alter glass coatings irreversibly so storing the lenses in a dry environment/sealed case with dessicant for preventing it is a good measure.
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Old 29-01-2012, 05:08 PM
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Yes, Mark, the coating is slightly damaged.. but now it is way better than it was... I am storing it in dry place and actually I killed all the fungus with UV last year - so there was no change in performance since.
However, I was using the lens in the meantime - and only if I stretched the image a lot (to get out the faint details of nebulae for example) it became obvious that something was wrong with the lens - it was showing un-even background, the result of scattering the star light.
I am looking forward to some clear skies in Melbourne to test it.. it is cloudy now of course :-(

Last edited by bojan; 29-01-2012 at 05:21 PM.
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Old 29-01-2012, 05:14 PM
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If you killed the fungus it's good enough. It won't grow or do any further damage. I bought a lot of lenses off eBay and made sure that there was always an explicit mention of no fungus in the listing. There's a lot of reading available about this topic on the Pentax Forums and how to store those lenses. Fungus is a one way road unfortunately. If it's there the damage is already done. Having said that you'd need a lot of contamination to significantly deteriorate the image through the lens. You'll have a bit of light scattering, that's all. Nothing dramatic. It's not a show stopper. It's like surface scratches on the optics.
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Old 29-01-2012, 05:24 PM
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Quote:
Originally Posted by multiweb View Post
. ... It's not a show stopper. ...
That's exactly my way of thinking as well..
And for the fraction of price for the new lens. BTW, this particular lens is really good (@F5.6, external aperture of course).
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