Scratched lens

[derekh]

Just got a new lens that I bought through the mail and I notice that there is a scratch on it. The scratch is on the glass element that is in the rear part of the lens that is closest to the shutter, so it appears as if the lens got scratched when someone was unscrewing the rear part from the lens board. I'm not sure if the scratch is on the glass itself or if it is just the coating that is scratched.

How can I tell if it is the coating or the glass that is scratched? And there any way to predict if this will affect image quality?

 

[Dave Parker]

You should be able to look at it sideways in the light and see how deep the scratch is, also you can look at it under your loupe and should be able to see the depth of the scratch.

As far as image being effected, I doubt very seriously that you will notice it, where is the scratch located? if tword the outside of the lens, you normally will be stopped down and it would have to be a very large scratch to effect the image if located in the center of the lens, most of the time the effects of large scratches is a loss of contrast, and perhaps a bit of flaring. Scratches are great barginning points on price, but normally don't have alot of effect on the images. This of course is based on my experiance, others surely will have other experiances.

Dave

 

[noseoil]

I have a 90mm Super Angulon which has a mark on the front element, about in the center of the lens. If there is a problem with resolution, flare, contrast or anything else, I have yet to see it in an image. Try the lens and see how your shots come out. Chances are, it will be fine. Too bad the seller was less than candid about the condition. You might try contacting them to see if something can't be worked out on price. As Dave has said, an excellent opportunity for a bargain.

 

[Mongo]

If you look a the scratch through a loupe at a steep angle, you should be able to see whether or not the scratch has rough edges. (A strong light source opposite the lens from you will help.) If there are rough edges, the scratch almost certainly is into the glass. If the edges of the scratch are fairly straight, it's probably just the coating.

I know that some don't like the idea of a scratched lens, but I've used a few in my time and haven't had any problems to speak of. (I do have one lens that I know will show the effects of the damage, but it looks like it was sandblasted on the rear element and it might be useful as a portrait lens.) You might want to get some film shot with this lens quickly to see if there are obvious flaws. If there are, then it's time to work out a return. If not, it's time to bargain for some money back.

The common wisdom is that a scratched lens should be shaded carefully (with an appropriate lens hood or, for large format lenses, a strategically held dark slide).

Good luck.

 

[glbeas]

Another way to deal with a scratch of deep enough to be in the glass is to very carefully fill it in with india ink so the rough edges can't scatter the light and make a flare. There will be practically no other effect on the lens as far as exposure (unless the scratch covers half the lens ).

 

[Bob F.]

If this is an LF lens, you should be able to unscrew the elements from the shutter to have a closer look. As stated, the general consensus is that most scratches have little if any detectable effect on the image.

However, your scratch is close to the optical centre of the lens which is probably the worst location as the light is passing through its narrowest point so distortion and loss of contrast seems more likely. One common trick is to paint such marks with a fine black pen or India ink. This reduces any flare & distortion caused by the scratch and the loss of light is essentially too small to measure.

Run a test with the lens wide open (worst case scenario) and put the scratch in a bright sky if possible.

Bob.

 

[Digidurst]

I have a Fuji 210mm complete with a pit in the rear element. Yeah, it was an eBay lens. But so far I haven't had a single image where it has shown up or caused a problem. Hopefully, it will be the same for you