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05-19-2007, 11:28 AM   #1
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Is this lens (Tokina AT-X SD 400mm) cleanable?

Hi all,
I just won this lens off of ebay and got it today. Unfortunately it has a small amount of fungus on it (lensSpotCrop.jpg photo - palmor photos at pbase.com). I already sent an email to the seller see how we can work something out. My question is does anyone know if this lens can be opened up and cleaned? I'd really like to keep it (you all know how hard it is to find a decent 400mm prime lens right now). My hope is that it can be cleaned and I can get some money back from the seller).

Oh, its a small enough spot that I'm not surprised the seller didn't notice it (and it doesn't affect the image right now), I'm not sure I would have on one of my lenses before I put it up on ebay so I'm not mad at the seller (unless he ignores my email hehe).

Oh its a Tokina AT-X SD 400mm f5.6 (the latest model with the tripod collar).


Thanks
John

05-19-2007, 11:35 AM   #2
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Have you tried shooting with it yet? is the fungus noticable? Having said that, there's really no way anyone short of a trained repair tech can get in there, clean it, and THEN put everything back precisely....
05-19-2007, 01:06 PM   #3
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Yea, gorfmai is right. Fungus is a pain in the ass to clean and you gotta disassemble. There is also a very high chance of making the lens worse. Misalignment of the elements after cleaning to introducing dust into the lens cavity during the cleaning. If it doesn't show up, its best to just leave it. Just keep the lens in a dry environment and the fungus should stop growing.
05-19-2007, 04:48 PM   #4
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Hey john,
Here's an interesting link Fungi in Photographic Lens , probably more than you want to know. I got a vivitar 400mm I cleaned because of some haze but it only cost me $60 If it was an expensive lens I'd probably take it to a repair shop.
good luck

05-19-2007, 04:49 PM   #5
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The chances of that fungus affecting image quality is extremely low. Bear in mind that your camera has a crop sensor (1.5x) so if it did end up showing up on a film camera or a full frame dslr (not that pentax make one) it would be cropped out by the camera in your case.
05-19-2007, 05:03 PM   #6
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Fungus everywhere! :(

Dear fellow pentaxians.. I was so happy this morning to buy an M50/1.7 for only around 17 euros! I bought it since it seemed like a bargain (it just looked like it had lots of dust in the lens to me, thought i'd just clean it out some time). On closer examination however, the lens seems to be overtaken by the fungus pretty bad. I don't have any pictures atm to show how bad it is, but it is really bad, on every glass element, to the sides and the center of the glass elements as well.

When I then looked at my M50/2 closely, I also saw small traces at the sides of the glass (not every element). However, very negligible compared to the M50/1.7.

I tried shooting with both lenses, neither shows any problem (haven't checked yet on a computer screen, but 20x digital zoom on-camera does not show any unsharpness/spots/anything else bad ). For testing purposes I shot a white paper sheet using widest and smallest apertures.

Now I have a few questions (after reading online about fungi in lenses etc. (gosh it does scare me a bit! :S))..

1) Does pentax offer an affordable cleaning solution to this? (remember, both the M50 lenses were very cheap!! I'd rather get a mint one off ebay then paying 3x the amount for a cleaning to have the fungus come back some day)
2) Is it worth the cleaning in the 1.7 case? Is it even possible with that amount of fungus?
3) (most important imo) Is it true that the fungus tends to spread across lenses? If so, I can keep the 'infects' far away from my new lenses.
4) Do bodies become infected as well? I.E. fungus at the sensor? That would be very scary...

Please note that I'm not that hyper-sensitive to all things unclean near my camera.. I don't become overly paranoid about it, shooting pictures should stay fun and never stressful about some small stuff. As long as it does not affect the images it does indeed stay fun, that's why I'm actually asking!

Thanks for your replies in advance
05-19-2007, 05:25 PM   #7
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barendvl,

If its not showing up on the pictures then i wouldnt worry about sending it away to be cleaned (if they can be at all)

Once you get them onto the computer, could you post up the test shots you did with the 1.7?
05-19-2007, 05:37 PM   #8
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QuoteOriginally posted by -spam- Quote
barendvl,

If its not showing up on the pictures then i wouldnt worry about sending it away to be cleaned (if they can be at all)

Once you get them onto the computer, could you post up the test shots you did with the 1.7?
Will do tomorrow probably. Going to sleep now.. Just returned from a holiday to Malta. Probably post some pictures of that later this week!

05-19-2007, 06:26 PM   #9
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Original Poster
Hi all,
Thanks for the replies everyone!. As far as I can tell it doesn't affect the image (I'll know better tomorrow when I take it out for more shots), which I expected since it's so small and so far to the edge of the glass.

I know its probably impossible to tell but assuming I keep it dry what would be the guess on the over-under of it getting to a point where it would affect the image? Are we talking years or months?

Thanks again
John
05-20-2007, 02:01 AM   #10
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I took some shots of the lens (hard to do it btw.. Needs backlighting to see the fungus correctly...

And I took some paper, put it against a window and took a picture at F22 and F1.7.

Here are the pictures:

Fungus
F22
F1.7

I've left the latter two at full size uncropped so decided not to put them on here full-size as it would ruin the forums' structure.

I see I have a dust spot near the left side.. :O
05-20-2007, 11:24 AM   #11
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QuoteOriginally posted by palmor Quote
Hi all,
Thanks for the replies everyone!. As far as I can tell it doesn't affect the image (I'll know better tomorrow when I take it out for more shots), which I expected since it's so small and so far to the edge of the glass.

I know its probably impossible to tell but assuming I keep it dry what would be the guess on the over-under of it getting to a point where it would affect the image? Are we talking years or months?

Thanks again
John
While you con't see the fungus in your images (it's so far away from the focal plane that it is way OOF) it will have the negative effect of scattering light, thereby reducing contrast. A couple of tests which might show this:
- Take a photo in a darkened room, with a flashlight or other strong light source in the frame, against a black background. Be sure to give plenty of exposure; I'd take several shots spaced 1 EV apart. You may see a halo or other evidence of light scattering.
- Shoot a large sheet of white posterboard with a smaller sheet of black construction paper or black cloth covering about half of it, under strong illumination. Adjust exposure to 3 stops more than the metered reading off the white card. Look at the contrast of the black area against the white.

Good luck; I hope that your fungus problem is not too destructive of IQ.
05-20-2007, 04:29 PM   #12
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one way to stop anymore damage is to wrap the front of the lens in aluminum foil, shiny side in, and set it out in the sunlight for 4-5 hours. the uv will kill it. i've actually seen this almost turn the fungus clear. you want the sun to shine into the lens.
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