Dust, scratch or missing lens coating? Look at this

[Pirate]

This will make you think twice before you ever turn down a perfectly decent lens on the basis of a small amount of dust, flaked-off lens coating or a scratch on the front element.

Prepare to be amazed

[pakodominguez]

Apparently your friend Kurt had lots of spare time
About his test, I'm not surprised at all. The front element of my Dimage 7Hi got scratched by a drunk patron during an event; I never saw any quality degradation on the pictures I took after that incident. The critical glass is the rear lens: just a small scratch on the rear element will show up in any picture.

Regards

[David Kilpatrick]

It's not so simple. A retrofocus zoom resembles two lenses, the front bit is more or less like a wide-angle converter. I was taking lenses apart and using only part of them when I was 13, I removed the front element of my dad's Zeiss Kolibri 50mm f/4.5 Novar and pushed the extending tube back into the body, to make a sort of vaguely OK 35mm f/3.5 lens.

The disappearing dirt is no more complex then disappearing cage wires at the zoo. Use a longer focal length, wider aperture, stuff on the front of the lens will just lower the contrast and not appear as an imaged flaw. Stop down to f/22 at 28mm and underexpose a close focused subject, and visible flaws would show.

Actually, the issue with old lenses is hardly ever down to single scratches or chips. They don't show at all in many designs, like fast standards or teles, but can be imaged if they happen with fisheyes etc. The real issue is a fine patina of scratches caused by too much cleaning of the lens over the years, using shirt tails or hankies etc instead of lens cloths. That can really take the edge off contrast and colour saturation - a sort of 'reverse CZ effect'. Little bits of physical damage to the front element may have no effect, invisible effects of bad cleaning technique can ruin a lens.

Lenses without either are preferable And try removing the front element of a telephoto, not a wide angle or standard - not even a macro lens! Not even a lens in most cases (no image forming ability).

David

[Dr. Harout]

Also use of any protective filter might hurt the shot more or equal to minor dust and scratch.