Impact of lens dirt & scratches on image quality

Discussion in 'Open Gear Talk' started by pdh, Apr 23, 2012.

  1. pdh

    pdh SC Legend

    Jan 2, 2011
    • Like Like x 2
  2. BillN

    BillN SC Hall of Famer

    Aug 25, 2010
    S W France
    Bill
    as I understand it - buy lens with scratches on front element really cheap as they have no or very little effect on IQ, (for us humans!)

    Paul, Arne today, (in the rain), if I can persuade my wife!!!!
     
    • Like Like x 1
  3. Brian

    Brian SC Top Veteran

    638
    Jul 7, 2010
    Internal haze is "IMO" the worst offender to image quality. It can cause color shift and loss of sharpness.

    I had a Summarit with internal haze, sent it out to be cleaned. Big difference in quality.

    Cleaning marks on the front element cause the least impact.

    I have a 90/2 Summicron with a fracture in the second element a few millimeters long. No real problem on the image unless in direct sunlight. Pixel-Peeping, you can find a minute effect.
     
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  4. pdh

    pdh SC Legend

    Jan 2, 2011
    i was counting myself as one of the obsessives Brian :smile: ... though the seller in question was not the one I had returned a lens to because of severe haze ...

    Bill - take your 10x bins if you're going to the hide although today the rain will make visibility a bit of a 'mare down there
     
    • Like Like x 1
  5. defektive

    defektive SC Veteran

    375
    May 4, 2011
    Tasmania, Australia
    Sam
    Great article and test, I will certainly consider "bargain" lenses with a bit more confidence. I am with Brian though, haze does have a big influence on the optical performance of a lens.
     
  6. bartjeej

    bartjeej SC Hall of Famer

    Nov 12, 2010
    bart
    wow I never expected those results to be so good!
     
  7. lenshoarder

    lenshoarder SC Veteran

    383
    Mar 7, 2012
    This has been around for ever. It is true though. I personally am not one of those people that need to go into a clean room to clean off their lenses. I use my shirt. The qualifier to this I'll add is isolated bits of dust and dirt don't degrade IQ that much. Lots of fine scratches, like on the coating really do though. It's all just foggy.
     
  8. pdh

    pdh SC Legend

    Jan 2, 2011
    well, since 2009 anyway, but I hadn't seen it before and thought perhaps others hadn't.
     
  9. Isoterica

    Isoterica SC Hall of Famer

    Dec 6, 2011
    The lens of my Ansco Memar Pronto lens is so hazed up the photos look like something shot with a pinhole, has a very dreamy effect. This favorable result is probably not the norm but I had several people want to buy the camera because of it. Nope I haven't sold it :D
     
  10. HeatherTheVet

    HeatherTheVet SC All-Pro

    Apr 23, 2011
    Scotland
    Heather
    I have a problem with little black specs on my photos, but I suspect it is bits of stuff between the lens and the sensor. I find it quite hard to keep everything clean and clear.
     
  11. lenshoarder

    lenshoarder SC Veteran

    383
    Mar 7, 2012
    If you can make them out as little black specs, then it's on the IR filter over your sensor. Use a handblower and blow them off.
     
  12. BillN

    BillN SC Hall of Famer

    Aug 25, 2010
    S W France
    Bill
    take a photo of a white wall at your highest f value - f32 and post it - probably dust on the sensor which is easily removed


    (Edit - as lenshoarder suggests above)
     
  13. HeatherTheVet

    HeatherTheVet SC All-Pro

    Apr 23, 2011
    Scotland
    Heather
    Thanks, I do try to blow them all away but I seem to collect more every time I change lenses. It's nice to know exactly where the problem is though, I'll stop obsessively cleaning the front glass now! The big prob is I can't see them at the time, only later when I get the pics uploaded. I guess I just need to be a bit more careful.

    I spotted a whole load of dandelion heads today at just the right stage for playing macro photography. I might nip out later and pick a couple up - I've never tried that classic shot yet.
     
  14. Isoterica

    Isoterica SC Hall of Famer

    Dec 6, 2011
    Make sure to get a shot of the sun behind them.. makes an excellent halo and really accentuates the details.
     
  15. HeatherTheVet

    HeatherTheVet SC All-Pro

    Apr 23, 2011
    Scotland
    Heather
    Example of little black specks. There's one above the cloud on the right. What really annoys me is when I take a pile of pictures in a row, and these blobs are on them all in exactly the same place. Fixable but annoying! Cleanliness is the answer I suppose, difficult for one who spends so much time covered in a variety of unpleasant stuff.

    [​IMG][/url] Torridon by heather_t_vet, on Flickr[/IMG]
     
  16. pdh

    pdh SC Legend

    Jan 2, 2011
    yep that's sensor dirt as others have said. this was at f/13 - bet you can't see it at f/8 or below though?

    if you can't blow it off with a rocket puffer then it's time to invest in either a sensor cleaning kit or take it into a photographic shop who'll clean it for you
     
  17. HeatherTheVet

    HeatherTheVet SC All-Pro

    Apr 23, 2011
    Scotland
    Heather
    I *think* I've got it clear now. If not I might take a wee trip into town and speak to some camera peeps. Interesting point about being able to see it at wider f/, never thought about it but all the blobby holiday pic were in France in bright sunlight so stopped down.

    To celebrate the discovery of what they are and what I need to do I have bought a new lens on ebay - Canon FD 135mm. Just because. £15 inc postage :)