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front lens coating removal?

 
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Sun Feb 17, 2002 6:13 am    Post subject: Reply with quote

Here's a maybe dumb question...
I just recently bought a very bad lens. On purpose! Has a good shutter to replace an ng one I already had. Anyway, it made me think about the front lens surface. They frequently suffer from severe scratches from cleaning or abuse, mostly just in the coating. Apparently causes not too much of an affect on film unless it's side lighted ( I have another lens with 'slight' cleaning scratches). But what if the coating was removed altogether? No more scratches and a clear lens. I've heard much about being careful about cleaning fluids to not damage the coating, but never heard of anyone ever intentionally removing the coating. Is this possible or practical? Is there any solution that would completely remove the front coating? I wouldn't mind trying this on the new lens since it's in such bad shape. So bad it doesn't need side lighting...
Anyone know one way or the other?
Thanks,
Rich...
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Dan Fromm



Joined: 14 May 2001
Posts: 1884
Location: New Jersey

PostPosted: Sun Feb 17, 2002 3:05 pm    Post subject: Reply with quote

Quote:

On 2002-02-16 22:13, RichS wrote:
Here's a maybe dumb question...
I just recently bought a very bad lens. On purpose! Has a good shutter to replace an ng one I already had. Anyway, it made me think about the front lens surface. They frequently suffer from severe scratches from cleaning or abuse, mostly just in the coating. Apparently causes not too much of an affect on film unless it's side lighted ( I have another lens with 'slight' cleaning scratches). But what if the coating was removed altogether? No more scratches and a clear lens. I've heard much about being careful about cleaning fluids to not damage the coating, but never heard of anyone ever intentionally removing the coating. Is this possible or practical? Is there any solution that would completely remove the front coating? I wouldn't mind trying this on the new lens since it's in such bad shape. So bad it doesn't need side lighting...
Anyone know one way or the other?
Thanks,
Rich...

John Van Stelten, who does business as Focal Point Optics (I think), recoats lenses. (sorry, URL not ready to hand). I'm not suggesting that you have yours recoated, but he may be able and willing to advise/discourage you.

Cheers,

Dan
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Sat Mar 09, 2002 5:52 am    Post subject: Reply with quote

Just an update for the curious...

Since this particular lens is pretty much junk anyway, I went at it using my experience in polishing brass & steel...

First some rubbing with solutions being worried about damaging the lens. Window cleaning and/or 90% alchohol had no affect whatsoever. Then I started polishing with a cloth and toothpaste (a very effective polish for such things). No affect noticable. Then toothpaste with a Dremel and felt polishing wheel. Cleaned the lens beautifully but didn't look like it would ever remove the coating. Added some talcum powder to the toothpaste, didn't help... Gave up being nice...
Went to a scrap piece of leather and jeweler's rouge and a good rubbing by hand. This worked perfectly! A wonderful polish and removed the coating. A bit or work by hand but not enough to move over to the Dremel.
So removing a lens' coating is actually pretty easy if needed without damaging the glass. Unfortunately, _this_ glass was the problem all along. Pits and scratches very deep into the glass. Not even going to try regrinding the lens. Well, not now anyway But I thought I'd finish up the topic by letting eveyone know how to easily remove the coating. I just wouldn't suggest anyone do it on my word alone
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hartwell_a_m



Joined: 04 Jun 2001
Posts: 84
Location: Northern California

PostPosted: Sat Mar 09, 2002 6:35 am    Post subject: Reply with quote

To minimise the difusion caused by the pits and scratches use india ink, jusr aply and wipe of the surface. The ink will not difuse the light passing through the lens and shouldn't show up on the negatives as light spots, unless the lens is severly gouged. BTW I found this information in an earlyer post, I dont remember when.
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Sat Mar 09, 2002 6:07 pm    Post subject: Reply with quote

Quote:

On 2002-03-08 22:35, hartwell_a_m wrote:
To minimise the difusion caused by the pits and scratches use india ink, jusr aply and wipe of the surface. The ink will not difuse the light passing through the lens and shouldn't show up on the negatives as light spots, unless the lens is severly gouged. BTW I found this information in an earlyer post, I dont remember when.

Yes, that's a great idea! I know the old trick of using a black wax on lenses to "get rid of scratches", but wax & photo lenses are a bad combination. Never thought of ink. I'll give that a try since I have a "test lens"
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