Micro scratches - What do they do to a lens?

[Ramiro Elena]

I have an 8 1/4 IN Goerz Celor I got for the Packard Shutter it came with. The lens has evidently not been cared for but it doesn't have nicks or scratches. It does have tiny micro scratches from (I guess) rubbing or maybe cleaning. They are all over the front glass.

Since I don't have a similar lens to compare I was wondering if anyone knows what these defects may do to the image and in which conditions they may be more evident (light conditions or distance to subject.) Is it a matter of contrast or even resolution or detail?

Thanks.

[Jim Jones]

If the scratches are bad enough, they increase flare and cause reduced contrast, especially in shadows. An efficient lens hood such as a compendium helps performance. So does keeping bright light sources out of the picture area. Such a lens might still have fairly good resolution. What might be a terrible lens for some photographers might suit others perfectly. Try your lens in a variety of situations. It may well have a place in softening wrinkles in some sitters.

[buggz]

Can't this also cause veiling glare, and halos?
Not knowing, just asking...

[evan clarke]

Make a couple of negatives and see how it looks..

[BrianShaw]

Often those cause no noticable effect.

As Evan said...

And, use a lens hood/shade.

[Hermes07]

As long as your lens is properly shaded (which it should always be anyway if you care about contrast and image quality) then I doubt you'd see one trace of a problem on the negative under a scanning electron microscope.

A lens' power and correction comes from its shape & thickness. To what degree does a micro scratch change the shape or thickness? a thousandth? a millionth? a trillionth? then consider what proportion of the surface area of the lens the scratch covers. Boils down to nothing.

[Ramiro Elena]

Thanks for the answers! I have actually made a couple shots with it.

Here's one, wide open at ƒ5 on Foma100.

Horacio Elena por rabato, en Flickr

Moreover, I have tried a Wollensak Velostigmat with a 1,5 cm deep scratch right in the middle of the lens that produced the following image.

Wide open at ƒ4,5 with the same film and similar light conditions.

Gaultheria Procumbens por rabato, en Flickr

[Joseph Dickerson]

Ramiro,

I have a Commercial Komura that has the same issue, and like you, I don't perceive any degradation of the images. Either there isn't any, it'll only show up in very specific circumstances, or, it's there and I'm not sophisticated enough to see it.

Pick any two!

I nearly always use a shade/hood with all my lenses, so maybe that's the answer. I've been taught that it can't hurt, but it can help.

Thanks for posting this and confirming what I've thought all along.

JD

[Hermes07]

Thanks for the answers! I have actually made a couple shots with it.

Here's one, wide open at ƒ5 on Foma100.

Horacio Elena por rabato, en Flickr

Moreover, I have tried a Wollensak Velostigmat with a 1,5 cm deep scratch right in the middle of the lens that produced the following image.

Wide open at ƒ4,5 with the same film and similar light conditions.

Gaultheria Procumbens por rabato, en Flickr

Ramiro,

I have a Commercial Komura that has the same issue, and like you, I don't perceive any degradation of the images. Either there isn't any, it'll only show up in very specific circumstances, or, it's there and I'm not sophisticated enough to see it.

Pick any two!

I nearly always use a shade/hood with all my lenses, so maybe that's the answer. I've been taught that it can't hurt, but it can help.

Thanks for posting this and confirming what I've thought all along.

JD

Not to claim there is be a problem as I'm still certain there won't be, but if a scratch or other surface defect were to show up it would be at minimum aperture not maximum. You could stick a postage stamp in the middle of the lens and have it not show up if you're shooting wide open.

[jcoldslabs]

I know a fellow photographer who shoots with a very beat up Aero-Ektar. It has a deeply abraded area about 1/8" wide and 1" long down the middle of the front glass, plus many, many small scratches front and back. He shoots with it only wide open and while there may be a slight contrast reduction, there really is no noticeable image degradation. I have to say this has surprised me.

Jonathan