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What is impact picture quality if a lens damaged what is not
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PostPosted: Fri Jul 18, 2008 9:42 pm    Post subject: What is impact picture quality if a lens damaged what is not Reply with quote

I would like to see here shared knowledge base from damaged lenses.

In my experience one or two deep scratch on front lens not impact picture quality at all if you not use lens in infinity distance, they are perfect in close-up and portrait distance.

Only one scratch on super-wide angle lenses can make it flare as Orio said to me.

On rare lens scratches impact picture quality above F11-F16 only.

Lot of scratches what is reduce the light path like haze or mold impact picture quality lens will be soft or/and contrast less.

Some fungus spot also not impact at all and if you store right it will not grow any more.


Broken glass if braked at edge also not impact quality on crop cameras.


PostPosted: Sat Jul 19, 2008 7:51 am    Post subject: Re: What is impact picture quality if a lens damaged what is Reply with quote

I hear that if you a scratch gives flare, fill it with black colour and it fix it. Never tried myself though


PostPosted: Sat Jul 19, 2008 8:09 am    Post subject: Reply with quote

In theory all scratches diminish the optical performance, in practice this might become more or less perceivable by human eye. Two important factors are the proximity to the film/sensor plane, and the focal lenght of the lens.
The nearer a scratch to the film/sensor plane, the more focused it will be. This is why a scratch on the rear lens is often worse than a scratch on the front lens when it comes to actually "see it" in the image.
However, I was sold by a Sicilian once, a Distagon 18mm lens advertised as perfect, with a big (I mean BIG) scratch exactly in the centre of the front lens. Not only it was visible as flare at all apertures (even wide open), when stopped down, it was visible also as a shape.
Of course in that case the short focal lenght of the lens made the problem worse than it could be on a tele lens. A super wide angle reaches a virtually infinite depth of field quite easily. So all optical problems on the surface of the glass can easily be spotted.

As a general statement I think it can be said that on tele lenses scratches have less of an impact than on super wide angles. However, under certain conditions, like shooting against the sun, and stopped down, even scratched on tele lenses can cause visibile problems.
Of course, they most certainly impact performance also at wide open, but the other factors (long focal lenght and distance from film/sensor plane) reduce the consequences to a point that an human eye can hardly tell a difference, except perhaps when comparing two photos at big enlargement (one made with scratched lens the other by intact lens)


PostPosted: Sat Jul 19, 2008 2:45 pm    Post subject: Reply with quote

Forgive my ignorance, but I had, in the later years, some lenses with

scraches, fungus, marks, etc, only in the frontal element. The pics taken

with them haven't any mark till I could see. I saw them with a lupe 30X

(slow diapo film). Now I have a super wide angle with lot of cleaning

marks, not scraches but with marks of fungus, all in the frontal element

only. I use the lñens at F/8, 11 and 16. Beleave me, not sign of them in

the film. I can't explain why or why not it occur, or what the theory say in

this question, I only know that when I see the pics at the 30 X lupe, I

don't distinguish nothing wrong.

Ohh.......visual problems you say? Crying or Very sad


PostPosted: Sat Jul 19, 2008 3:43 pm    Post subject: Reply with quote

@estudleon

Orio is right and you can check it by yourself.

I once forgot to clean the back of my Nikkor 18-55 (fantastic lens for the price btw even if it's AF) and while at 55 I couldn't notice any problem at 18 I could see in the viewfinder the dust that was in the back lens.


PostPosted: Sat Jul 19, 2008 5:07 pm    Post subject: Reply with quote

Atilla, This is my experience too. But, after you have collected many lenses - more than you can use in one day - it's nice to buy only the unscratched ones Smile


PostPosted: Sat Jul 19, 2008 5:10 pm    Post subject: Reply with quote

Yes nice to buy beautiful mint one, but pretty shame to think a lens is garbage is scratched and nobody want to take them.


PostPosted: Sat Jul 19, 2008 11:23 pm    Post subject: Reply with quote

[quote="A G Photography"]@estudleon

Orio is right and you can check it by yourself.

I once forgot to clean the back of my Nikkor 18-55 (fantastic lens for the price btw even if it's AF) and while at 55 I couldn't notice any problem at 18 I could see in the viewfinder the dust that was in the back lens.[/quote]



Wow, my visions problems are really serious. I need lupe of 50 or 60x to

see my diapo Shocked