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Cleaning a very dirty lens


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#1 David Hefner

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Posted 07 October 2006 - 02:56 AM

I'm trying to be careful about what I post in that I search the forum for my answer before I do so. I think I found my answer, but I want to make sure for this particular case.

I just bought a new Bell & Howell 70-DR in great working order. However, upon examination I noticed both lenses, the 1' and 3', are very very dirty. When I remove them from the camera hold them up to the light I can see lots of dust and large specs of dirt. Today I bought some lens cleaner and paper but I'm worried about scratching.

How do I effectively clean these lenses without scratching? Should I first use a brush and than the lese paper? Keep in mind, this dust has probably been there for some time and might not brush away easily. Are Q-tips okay for the hard to reach parts? Or maybe a wet tooth pick covered with the lens paper?

Thanks guys.
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#2 didier Frateur

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Posted 07 October 2006 - 08:26 AM

Don't use a brush, nor the tooth pick. Just roll one sheet of lens cleaning paper, tear it into two parts, moisten the 'cut' soft part with lens cleaning fluid and use that as a brush. Start in the middle of the lens and gently move it slowly towards the edge, making circles. The dust should stick to the paper, or be removed towards the side. You can repeat this as many times as necessary, using a new piece. Don't be affraid to use some pressure if necessary, lenses and coatings are quite hard, unless you have to deal with sand or similar dirt. In that case you will have to blow them away first with a small and controlled amount of air.
To remove eventual dry marks of the lens cleaning fluid, you can use a new piece of chamois leather, or another clean, soft cloth (for cleaning glasses) making the same circular movements.
Your lenses should come out like new, unless they were scratched before, or if coatings were affected by acid marks like fingerprints..
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#3 Dan Salzmann

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Posted 07 October 2006 - 11:30 AM

Many soft cloths for cleaning eyeglasses contain silicon compunds that are not recommended for lens coatings. Are these large pieces of dirt inside the lens?
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#4 Robert Hughes

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Posted 07 October 2006 - 02:19 PM

Follow the above posts for cleaning the front and back elements, also take a look on the Schneider site, they have a good description of proper lens cleaning procedure. Start with the least invasive technique possible, and move on to stronger methods only if the earlier methods don't work.

I've owned a few Filmos and have often seen black specks inside the lenses where I can't clean them. Ignore them, they are just bits of black paint that flaked off the shell onto the lenses. If you have mildew or mold between the elements you've got a problem - mildew etches the glass elements so that the damage is almost impossible to remove. And mold can spread to other parts of your camera, so you may prefer to keep moldy gear seperated from anything you still value. But I've seen some pretty screwed up lenses provide usable images, so don't write off your set yet.
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#5 David Hefner

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Posted 09 October 2006 - 01:29 AM

Okay so I cleaned the lens as described and all the dirt and dust has been removed but when I take the lens off the camera and hold it up to the light I can see a thick film along with two small scratches. The film must be inside the lens. I guess the scratches must have been there before but just covered by the dust. I do also see one black spec in the middle but I guess this doesn't matter based on what was said.

So is the lens useless now? Can it be saved? Should I take it into a shop and have it serviced or should I just buy a new 25mm lens?
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#6 Bernie O'Doherty

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Posted 09 October 2006 - 07:33 AM

Hi, David,

It all boils down to pricing really. If the lens isn't worth much to begin with, you're not going to want to get a bill for a couple hundred dollars for cleaning, servicing and collimating/calibrating. The problem with a lot of these older lenses is that they don't have the newest coatings and people generally paid very ltitle for them.

If you feel that this lens is in decent shape and you like it, it might be worth while taking it to a good tech for a check up and interior cleaning, etc. (hopefully to a place where the estimates are free and the prices reasonable).

I suspect that the thick coating you speak of is a combination of evaporation of oil ingredients mixed with dust that the lens pulled in over the years on the inside. Generally if a scratch is not in the middle of the lens, it is not troublesome. However, if you have side scratches and the light hits the front of the lens obliquely, it can cause flaring. The black speck on the inside would be easy for any good tech to remove.

Cheers,
Bernie
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#7 Charles MacDonald

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Posted 09 October 2006 - 08:04 PM

Hi, David,

It all boils down to pricing really. If the lens isn't worth much to begin with, you're not going to want to get a bill for a couple hundred dollars for cleaning, servicing and collimating/calibrating.

I have gotten a few of the B&H one inch lenses by buying a 16mm Magazine camera for 30 bucks of less on e-bay. If you allow a 50% failure rate, that still means that you would not want to speend more that 75 bucks to get it checked out.

If you have an olld used camera shop in your neighbourhood, you may be able ot find a 1 inch COMAT lens with some return privledge for 20 bucks or less.
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