Helpful Posts Helpful Posts:  0

View Poll Results: can you see the concentric ripples top left?

Voters
6. You may not vote on this poll
  • yes, clearly

    0 0%
  • no or only by squinting etc

    6 100.00%
Results 1 to 12 of 12

Thread: axial colour aberreration & correction thereof

  1. #1
    crisscross's Avatar
    Join Date
    May 2008
    Location
    Herefordshire UK
    Posts
    816
    Real Name
    Chris

    axial colour aberreration & correction thereof

    I took this shot with my 18-135 kit lens (not having anything else as I thought I was going to be doing sunset) only really expecting the foreground as an OOF silhouette, the sky dark and dismal and the moon, well much like a shot I posted here this time last year.

    http://img2.pict.com/d9/28/4a/2133034/0/dsc5607g.jpg

    However I found it possible to extract an image I am quite pleased with and actually showing for once more than the naked eye could see rather than less, BUT

    Especially in the top left corner there is some banding a bit like ripples on a pond surface which I can't quite get rid of - Nikon technical say they can't see them so the poll is to see who can, it does not seem to go away with different monitor calibrations as Nikon suggested

    The real question though is (assuming you can see it), what is the cause? I noticed for the 1st time that there is now in NX2 a 'camera & lens corrections'>axial colour aberration. Rather little info on exactly what that might be or do, but http://spie.org/x32840.xml hints at coatings on a cheapo lens being a possible.

    Anyone have any ideas please?

  2. #2
    Moderator Donald's Avatar
    Join Date
    Feb 2009
    Location
    Glenfarg, Scotland
    Posts
    19,661
    Real Name
    Just add 'MacKenzie'

    Re: axial colour aberreration & correction thereof

    Chris

    Yep. When I put it to the maximum size to which I can get it, I see a faint ripple starting slightly out from the top left corner and running at 45 degrees towards the bottom right.

    As to the cause, I shall defer to those with greater knowledge.

  3. #3
    arith's Avatar
    Join Date
    Sep 2009
    Location
    Burton on Trent, UK
    Posts
    4,786
    Real Name
    Steve

    Re: axial colour aberreration & correction thereof

    I can see dark lines on both sides; is that what you mean because they are all over the sky but mostly in left and right.

    I've only got a 720p monitor Samsung 2032BW which is calbrated with nVidia DirectX 9.0c and Phys X.

    I don't mess with the settings and let nVidia choose best settings.

  4. #4
    crisscross's Avatar
    Join Date
    May 2008
    Location
    Herefordshire UK
    Posts
    816
    Real Name
    Chris

    Re: axial colour aberreration & correction thereof

    Donald sounds as if he has it spot on, thanks Donald

    Arith -the flaw is concentric circles, I would roughly say lighter in tone than average, but that is subjective. Your monitor and calibration details don't mean a thing to me, but if you are saying it is only 720pixels wide, I doubt that can give a screen resolution appropriate to DSLR photography. This image is reduced to 1200x800 assuming my macBook screen 1440x900 is the minimum folks use today. If yours is carrying out a further reduction in resolution or being transferred by the host site to the 800pixels wide (or worse) version of image, it will be introducing a new range of artifacts....but thanks for your participation

  5. #5
    arith's Avatar
    Join Date
    Sep 2009
    Location
    Burton on Trent, UK
    Posts
    4,786
    Real Name
    Steve

    Re: axial colour aberreration & correction thereof

    No 720p HD 1680 pixels wide; but I can't see the circles then.

  6. #6

    Join Date
    Apr 2009
    Location
    Epsom, uk
    Posts
    186
    Real Name
    Will

    Re: axial colour aberreration & correction thereof

    i couldnt see anything, so i opened the image to expand the levels of the sky, and the only concentric 'ripples' i see are due to posterisation...

  7. #7
    crisscross's Avatar
    Join Date
    May 2008
    Location
    Herefordshire UK
    Posts
    816
    Real Name
    Chris

    Re: axial colour aberreration & correction thereof

    Quote Originally Posted by wjh31 View Post
    i couldnt see anything, so i opened the image to expand the levels of the sky, and the only concentric 'ripples' i see are due to posterisation...
    I do not usually use the PS type levels control, but I have looked at it and see that the input looks as if there is nothing in the right hand third. However looking at the enlarged 3 colour histogram which is the 'master' analysis tool in NX2, there is in fact a little triangle at the extreme right representing the moon....hence it is not appropriate to expand the levels

    I may not have made myself clear, but what I am after is
    (a) to know how it appears to other forum members as processed , ie having eliminated the phenomenon as near as I can manage on an image reduced to 1200x800 and 300kb. On nef FS I doubt I would spot it had I not been aware of it in processing. It doesn not show on an A4 print. Reduced to 720w/200kb limit on another forum I know that identifiable posterisation ensues, but that shows more below the moon
    (b) what causes this particular pattern, which I have never come across before, but I suspect is caused by pushing a cheap lens too far. Nikon reduced the range to 18-105 after the D80 and it is well known that at 135mm and small apertures, there is a pronounced vignette.

    Another possible cause is removal of the said vignette; it still seems to be present even if one zeroes the vignette control - but it could be that the software sets the zero point with some vignette reduction

    For those withpout exif viewing tool this is D80, 18-135 kit lens at 125mm, ISO 200 f7.1 at 1/200
    Last edited by crisscross; 5th December 2009 at 05:16 PM.

  8. #8

    Join Date
    Oct 2009
    Location
    USA - California
    Posts
    445

    Re: axial colour aberreration & correction thereof

    Couldn't see anything wrong; I'm on a calibrated/profiled monitor here.

  9. #9

    Join Date
    Dec 2008
    Location
    New Zealand
    Posts
    17,662
    Real Name
    Have a guess :)

    Re: axial colour aberreration & correction thereof

    Hi Chris,

    All I'm seeing is some barely perceptable horizontal banding slightly below 1/2 way that goes through roughly a single "sine wave" from left to right.

    Easiest to see if I move the image up and down with a scroll bar.

  10. #10
    Moderator Dave Humphries's Avatar
    Join Date
    May 2008
    Location
    Windsor, Berks, UK
    Posts
    15,991
    Real Name
    Dave Humphries :)

    Re: axial colour aberreration & correction thereof

    Hi Chris,

    I'm not really seeing anything that I couldn't say wasn't just variations in the sky (misty cloud style).

    Not sure that helps much, but as you say, we are looking at an image in which you have minimised the problem - very successfully I'd say.

    Cheers,

  11. #11

    Join Date
    Aug 2009
    Posts
    2,342
    Real Name
    Steve

    Re: axial colour aberreration & correction thereof

    Quote Originally Posted by Colin Southern View Post
    Hi Chris,

    All I'm seeing is some barely perceptable horizontal banding slightly below 1/2 way that goes through roughly a single "sine wave" from left to right.

    Easiest to see if I move the image up and down with a scroll bar.
    Thats exactly what i see as well.

  12. #12
    crisscross's Avatar
    Join Date
    May 2008
    Location
    Herefordshire UK
    Posts
    816
    Real Name
    Chris

    Re: axial colour aberreration & correction thereof

    OK thank you all on part (a), unfortunately depriving all but Donald of a potential example!

    So what about part (b) does anyone either know enough about "axial colour aberration" to give a quick run down, or other URL where it is treated at a level for photographers rather than folks with degree in optics?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •