Scratched Lens Blues

[Porter]

I recently purchased a Canon Auto Zoom 518 Super 8 Camera from a flea market (where else?). I was dismayed and a bit embarrased to discover that that lens had a fairly bad scratch in it. Since the price I got it fo rwas pretty good, I'm wondering what the possibilities of repairing it are. Is there something you can rub on a lens to help correct it? Should I look for a replacement and if so, are they easily replaced?

[wahiba]

Assuming it is a lense, and not a cover glass that is scratched. Any elimination with an abrasive will alter the lense geometry, with dire results.

Have you tried a film it it? It might not be noticeable.

[tim]

Given that the area affected by the scratch is much smaller than the total area of the lens, there will be two effects:

1. Image contrast will be slightly reduced by scattering (and very bright lights in the frame may have odd-shaped, faint, diffraction patterns around them).

2. There will be a slight reduction in effective f number.

Scattering can be eliminated by carefully painting over the scratch with a photographic black or blackboard paint with a fine brush. If this is done carefully, with no more line width than necessary, the image on the film should not be noticeably affected, and the faint diffraction pattern around very bright lights will be reduced too.

Check to see that the line over the scratch does not appear as a shadow at minimum distance focus.

[BolexPlusX]

I have a Super-8 camera with some kind of lines on the inside of the objective lens. They seem to be a crazing in the coating and look a little like a spider web. This is only visible from an angle; from straight ahead the lens is clear.

I initially considered dissasembling the lens and trying to remove whatever it is, but I've shot some film with the camera and the resulting image has nothing funky about it-so I'm leaving it alone.

Anybody know what this is?

[Guest]

Here's a website that explains it all:

http://www.chem.helsinki.fi/~toomas/photo/fungus/

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[Porter]

Thanks for the advice!

Yes, I think that the next step is to shoot some film through it and test it out. The scratch almost disapears through the viewfinder (which goes through the lens), but the true test will be seeing it projected.

It is definately a scratch and not fungus, although now I'll check for the telltale web patters too. And it is indeed on the lens.

Are these lenses difficult to replace?

[mike]

Didnt you notice the scratch before you bought it?

Scratches on lenses usually dont show up, unless you shoot wide and into lights.

Fungus can be cleaned by taking apart the lens or soaking it in alcohol.

[Lucas Lightfeat]

Taking apart a lens will almost certainaly bollocks up your collimation, which will be imposible to reset, resulting in almost all shots being out of focus.

My suggestion is that you buy another camera and put it down to experience. I have shot about 70 rolls on 2 Canon Auto zoom 518's I've owned, and they're very nice, but not particularly special cameras. Check out ebay - if you're going to spend ¥€£$$$ on film, you might as well get a camera that hasn't got a scratched lens. It's really basic to good images!

Lucas