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Old Aug 18, 2006, 7:28 PM   #1
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Hi,

What is this likely to meanregarding the performance of the lens? Will it affect picture quality ina similar way to when there is dust on the sensor - ie blurredspots when shooting a plain background (We hadthis problemon our new K100D but fortunately theOz distributor,CR Kennedy replaced it with a new body - I was impressed by the service).I have seen a couple of Pentax SMC 50mm f1.7 / f1.4 Prime lens on ebay with this type of descriptionand they are cheap.I want to get one of these primelens to play with and am not fussy about perfection as long as picture quality would still be good.

Thanks,

Bob
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Old Aug 18, 2006, 7:44 PM   #2
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One other question....

The best way I found to display the effect of the dust on the sensor was to take photos of a blue sky where they showed as a small round blurry shadow.

Would taking a picture of a blue sky also show any effects of dust / fungus in the lens?

Thanks,

Bob
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Old Aug 18, 2006, 7:53 PM   #3
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Bob-

Here is what I do. If the lens is not clean and clear, if the aperturedoes not readily snap into position when changed, or if the aperture control is not fully operative. I simple walk away. IMHO that is not a lens that I want to spend my time trouble shooting. Just a personal opinion, your mileage may vary.

MT/Sarah
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Old Aug 18, 2006, 9:06 PM   #4
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I recently bought a Vivitan 75-205mm f:3.5 from an on-line auction. The description said there was dust in the lens, well there may well have been dust but there was also enough mushrooms to feed all of Santa's elves for a year.

At first I was very angry at the vendor and at myself for having wasted my money but instead of staying angry I took advice on-line, opened it up one afternoon, washed the optics in alcohol and now I am very pleased with myself.:G

If I saw a lens such as a f1.4 prime, especially if it were Pentax, described as having any fungus at all I would make a very low bid and hope it came my way, even if I could not fix it I would not be downhearted.


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Old Aug 18, 2006, 9:27 PM   #5
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bob,
welcome to the forum.
your sensor method is right on the money.. just cleaned mine today twice. that's after changing lenses in the car and a week in the desert..

fungus and mold is a lot harder to tell if it will affect the image unless you have the lens in hand. i recently sold ira a A70-210 that i bought when it was listed as having the focus frozen but with perfect glass.. yeah right. the focus was frozen and it was easily remedied but the lens had noticable fungal damage. i killed what ever fungus was in it and checked it out and found no image degradation. i bought it for 24usd and sold it to ira for 45usd. gawd, i made about 10usd for the trouble.. i've seen this same lens sell for over 200usd on ebay since.. i've also bought ''perfect lenses'' for nothing and they are contributing to my knowledge of lens reconstruction.hehe

you may get lucky and you may not. it just depends on the amount of damage.. you take your chances and you pay the price. if the lens is listed as optically perfect or without fungus and clear then you have a legitimate basis to stand on.
dust in the lens is not a major problem. ALL older lenses are going to have it, especially the push/pull zooms. don't worry about a small amount of dust. it really takes some major damage to a lens to actually affect the image quality.

guess that didn't really help,
roy
edit: ANY COMPLAINTS IRA??????
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Old Aug 18, 2006, 9:33 PM   #6
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John Hill wrote:
Quote:
I recently bought a Vivitan 75-205mm f:3.5 from an on-line auction. The description said there was dust in the lens, well there may well have been dust but there was also enough mushrooms to feed all of Santa's elves for a year.

At first I was very angry at the vendor and at myself for having wasted my money but instead of staying angry I took advice on-line, opened it up one afternoon, washed the optics in alcohol and now I am very pleased with myself.:G

If I saw a lens such as a f1.4 prime, especially if it were Pentax, described as having any fungus at all I would make a very low bid and hope it came my way, even if I could not fix it I would not be downhearted.

john!!
we were posting at the same time. any links to diassembleing a lens would be HIGHLY appreciated. also your experience and methods would be also..

yeah!! i know about the mushrooms!!

roy
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Old Aug 18, 2006, 10:30 PM   #7
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Thank for all the advice.

John, I will follow yoursuggestionand bid low on the f1.4. If Iwin itand itis in bad shape Imight have to come back to you to get some pointers on how to clean it up!


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Old Aug 19, 2006, 12:20 AM   #8
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He sent me a photo taken through the lens. I guess the white "fur" is the fungus. Is this likely to affect a photo or to get worse to the stage where it would?

Would it be easy to clean?

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Old Aug 19, 2006, 3:35 AM   #9
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Roy, Bobinoz, until I tried it I had never seen the inside of a lens of any kind except a few weeks ago when I changed the mounting on a Sigma400 f5.6and the only time I had seen the inside of a camera was to change the lens or the film!

However someone on line, I think it was even this site, sorry I forget the posters' name, suggested I try to fix it and treat it as a learning experience.

So all I did was put aside an afternoon with a clean workspace, a good light and a set of small screw drivers. The only piece of specific advice I had heard was that most lenses are opened from the front, not through the mounting end.

I examined the zoom lens barrel for screws, some were obvious and some painted over. I carefuly undid the screws trying to understand the function of the various threads and cams etc as the pieces came apart. Then I washed the lenses in alcohol and put it back together again and it works!:G

Someone said that only experts should try to dismantle a lens and someone else said lenses are assembled to very fine tolerances. This is probably true but when the lens is really worth nothing and you avoid undoing anything that looks like an adjustment then I say go for it.



Incidently, I tried to clean another similar lens today and all I managed to do was to twist the tip off a Philips screw driver and foul the screw head :sad:, oh well, onecant win them all.








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Old Aug 19, 2006, 8:01 AM   #10
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I would take Sarah's advise. Simply walk away. Have some patience and a clean one will show up on ebay.

In my book, a lens with anything behind the glass is only good when you get it for free.

TDN
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