| Author |
Message |
    
Krafty5260
Tinkerer
Username: Krafty5260
Post Number: 18
Registered: 02-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 07, 2008 - 06:27 pm: | 
|
Okay, I like to ask the simple questions as well as the tough ones, because it makes people wonder if I'm a dumb a**, or one clever bugger. You'll each have to decide that for yourselves.
When I see lenses advertised (separately, or on cameras) that argue,"one or two dust specs in lens that won't affect pictures," it makes me wonder, first, why won't it affect the pictures, and second, how bad does it have to be to affect pictures? And, what about "minor cleaning marks," or, "almost invisible scratches on the front lens element"?
When do I need to be concerned? Fungus I get. And, I saw a Perfex Fifty-Five with what appeared to be a bullet-hole through the lens. That, I could figure out for myself. But, seriously, what is so minor, one need not worry? Oh, BTW, any leads on a collapsible Tessar 3.5 for Contax II, et al, are appreciated, sans bullet holes, if it's all the same.
Thanks, gang,
Michael |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 554
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 07, 2008 - 07:28 pm: |
|
Dust specks generally won't have a measurable effect on photos unless they're just horrendous: the effect of a speck of dust is usually to absorb the light that hits it, preventing that ray of light from reaching the film.... so it becomes a function of the percentage of the lens area that's blocked by the dust specks, probably a small fraction of a percent.
Scratches, and particularly cleaning marks, are another story: they cover a much larger area of the surface than dust specks do, and rather than absorbing light they scatter it. The scattered light bounces around inside the lens and does reach the film, but not in the locations where it's supposed to. Its effect is generally to reduce contrast by scattering light into areas of the picture that are supposed to be dark.
And, if the performance of that Perfex 55's lens was similar to mine, a bullet hole probably wouldn't make it that much worse.....
: ) = |
Krafty5260
Tinkerer
Username: Krafty5260
Post Number: 20
Registered: 02-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 08, 2008 - 07:51 am: |
|
What a great and complete answer, Rick. Thank you. I'm left without any more questions - on this topic.
Michael |
Alex
Tinkerer
Username: Alex
Post Number: 55
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 09, 2008 - 03:19 am: |
|
Rick's spot on, as always.
How badly can a lens be damaged and still take good pictures? Try this:
http://www.certo6.com/gallery/planar.html
Alex |
Arnoldharris
Tinkerer
Username: Arnoldharris
Post Number: 34
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 12, 2008 - 03:01 pm: |
|
I looked at the linked photo of what appears to be a lens of the type you might want to throw away.
Then I looked at the gloriously gorgeous photo that had been taken using that lens.
One of the better wordless but appropriate answers I have seen in quite a few years.
Arnold Harris
Mount Horeb WI
Arn |
Glenn
Tinkerer
Username: Glenn
Post Number: 319
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 12, 2008 - 06:28 pm: |
|
In most cases you will find that lenses with cleanly cracked front elements, will produce very good images. Problems start to occur when you have 'flaking/chips' associated with the cracks - this can produce tremendous amounts of flare/distortion. The odd bug or two is nothing to be concerned about photographically. However the very thought that it is there, may cause one to worry needlessly about cleaning it out! |
|
