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Thread: That horrid CA

  1. #1
    arith's Avatar
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    That horrid CA

    This is a difficult job, a non HDR with lens wide open to minimise CA but look, still get a lot. Is there an application designed to remove it without loss of colour?

    Out of ACR without sharpening or noise reduction.
    That horrid CA

    Two hours later I called it a day.
    That horrid CA

  2. #2
    Moderator Dave Humphries's Avatar
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    Re: That horrid CA

    Quote Originally Posted by arith View Post
    This is a difficult job, a non HDR with lens wide open to minimise CA but look, still get a lot.

    Is there an application designed to remove CA without loss of colour?
    Hi Arith,

    I am fortunate that since moving to Nikon, I've never had it bad enough to fret over unduly. Therefore, I am no expert.
    Any I do get, I carefully remove with a desaturation brush.

    OK 3 possibilities I know of;
    1) Not much help
    I believe the (full) version of ACR that comes with Lightroom does have a CA correction tool.

    2) Still not much help to you (but may help others)
    I believe the Nikon ViewNX can fix it, perhaps Canon's DPP can?

    3) Might be some help
    I think DXOMark can import RAW and deal with CA, but I'm not sure if that costs money or not. I have never tried it.

    Unfortunately, (and I did just double check), the Filter > Correct Camera Distortions dialog in Elements does everything except CA

    Hopefully someone else will respond and be more help soon,

  3. #3
    Jim B.'s Avatar
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    Re: That horrid CA

    DPP has CA correction.I've not used it,but should do a decent job.

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    Re: That horrid CA

    Quote Originally Posted by Dave Humphries View Post
    I believe the (full) version of ACR that comes with Lightroom does have a CA correction tool.
    It's also in the "full version" that comes with Photoshop (or in other words, it's just not in the Photoshop Elements version).

    Seems to work OK.

    Other way around it is just to "do it the hard way" in Photoshop.

  5. #5
    Nik's Avatar
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    Re: That horrid CA

    oh wow.
    i think i may feel dumb in a second.

    what's "CA"?

  6. #6
    Moderator Dave Humphries's Avatar
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    Re: That horrid CA

    Quote Originally Posted by Nik View Post
    i think i may feel dumb in a second.

    what's "CA"?
    Nah, don't worry about it Nik.
    None of us knew before we started

    It stands for Chromatic Abberation; meaning - in Arith's first shot, the red/cyan edges most visible against the sky on the right edge of left wall and the gate metalwork. Colour fringing.

    It isn't always red/cyan, sometimes yellow/blue or green/magenta - it all depends on the lens.

    It is characteristic that a pair dark poles against the sky, one on each side of an image will show sky-red edge-post-cyan edge-sky and the opposite order on the right hand side of shot. It is because the lens has focused the red light at very slightly different magnification to the green and blue light. Thus it gives a red edge one side and the opposite colour to red (cyan) on the other.

    Often noticeable on shots with winter (bare) tree branches against the sky, some lenses can make these appear a nasty mush of magenta and green.

    Better quality lenses use special glasses and/or aspheric (specially shaped) elements to combat this feature - but then they cost more.

    Cheers,

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    Re: That horrid CA

    Quote Originally Posted by Nik View Post
    oh wow.
    i think i may feel dumb in a second.

    what's "CA"?
    Hi Nik,

    We tend to throw abbreviations around a bit here ... he's a few you'll come across ...

    LR - LightRoom
    PS - Photoshop
    PSE - Photoshop Elements
    ACR - Adobe Camera RAW
    HTH - Hope This Helps
    YMMV - Your Milage May Vary
    HDR - High Dynamic Range
    Nik - Nicole

  8. #8

    Re: That horrid CA

    Nik - Nicole ??? What's that?

    OK 3 possibilities I know of;
    1) Not much help
    I believe the (full) version of ACR that comes with Lightroom does have a CA correction tool.

    ACR does correct CA but it may introduce colour fringing
    in other parts of the image and in some cases, softening. It is also not entirely effective in severe situations. Guide: http://www.photos-of-the-year.com/articles/adobe-raw/

    2) Still not much help to you (but may help others)
    I believe the Nikon ViewNX can fix it, perhaps Canon's DPP can?

    ViewNX, to my knowledge, only removes purple and blue fringing.


    3) Might be some help
    I think DXOMark can import RAW and deal with CA, but I'm not sure if that costs money or not. I have never tried it.

  9. #9

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    Re: That horrid CA

    Quote Originally Posted by Blazing fire View Post
    Nik - Nicole ??? What's that?
    Nik's nickname, and her real name!

  10. #10
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    Re: That horrid CA

    The RAW processor Bibble (version 4 or 5) has very effective CA correction.

  11. #11
    arith's Avatar
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    Re: That horrid CA

    Cheers Colin and Dave and everybody; I can't have the full version of ACR unless you mean colour noise control which removes definition out of just about everything. DPP did remove CA but wasn't absolutely brilliant and Helicon Filter just removes all colours within a percentage of the CA.

    In the end I used a little CA reduction and a lot of colour replacement, it just took a long time. cheers

  12. #12
    arith's Avatar
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    Re: That horrid CA

    Quote Originally Posted by timo2 View Post
    The RAW processor Bibble (version 4 or 5) has very effective CA correction.
    cheers, I will have a look at that.

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    Re: That horrid CA

    Hi,
    Although I didn't see too much CA.I took Your first shot and spending not much time, I open it with Capture NX2 and corrected it(about 5 mim.)

    arith-1.jpg
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    Last edited by Dave Humphries; 10th April 2010 at 02:00 PM.

  14. #14
    arith's Avatar
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    Re: That horrid CA

    Ta, it took me two hours first trying ACR then DPP then Helicon Filter then tried DPP and Topaz Denoise then ACR..... In the end I repainted and where CA reduction caused a double outline used a squeezing tool.

    Unfortunately you can't see the full size here but I blow up 100% on my pc. Actually I'm surprised I didn't get flare but I shaded the lens with my hand.

    I'm always trying to get the impossible, the gate leading to the memorial and the sun outside, if I changed my lens it would be better but that is a major job (it was in a backpack on my back along with the tripod) and I decided I was just here to enjoy myself, I had already done my HDR. cheers

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    Re: That horrid CA

    Quote Originally Posted by arith View Post
    Ta, it took me two hours first trying ACR then DPP then Helicon Filter then tried DPP and Topaz Denoise then ACR..... In the end I repainted and where CA reduction caused a double outline used a squeezing tool.

    Unfortunately you can't see the full size here but I blow up 100% on my pc. Actually I'm surprised I didn't get flare but I shaded the lens with my hand.

    I'm always trying to get the impossible, the gate leading to the memorial and the sun outside, if I changed my lens it would be better but that is a major job (it was in a backpack on my back along with the tripod) and I decided I was just here to enjoy myself, I had already done my HDR. cheers
    Here,in my country,I learned to wear out a lot from little(because of the poverty).So I should not change the lens.I should try to assume "its mistakes" like mine.Of course none of us will not have to recognize that.Always there is an object which is guilty.

  16. #16
    arith's Avatar
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    Re: That horrid CA

    I've only just found out that CA can be two different colours in the same image. Worse, removing CA leaves an outline that looks like blur. I like short well defined shadows in my general direction and the very bright day look, but the only way I think I will solve this is with a lens with very high CA performance. I've already got one but it isn't wide.

    Here is red and blue CA with most of the red removed, my eyes are not really good and I didn't see the blue, in fact it helps me to print out because the monitor is bright.

    That horrid CA

  17. #17

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    Re: That horrid CA

    Quote Originally Posted by arith View Post
    I've only just found out that CA can be two different colours in the same image. Worse, removing CA leaves an outline that looks like blur. I like short well defined shadows in my general direction and the very bright day look, but the only way I think I will solve this is with a lens with very high CA performance. I've already got one but it isn't wide.

    Here is red and blue CA with most of the red removed, my eyes are not really good and I didn't see the blue, in fact it helps me to print out because the monitor is bright.

    That horrid CA
    Hi,
    You must take CAs like a given.My opinion is that your image is decent one from the point of view of CA.I took the flag and applied Capture NX 2 CA correction:red/cyan minus 37 and blue/yellow minus 6.
    The result is below, where no.1 is Yours uncorrected

    flag-12.jpg

    Radu Dinu
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    Last edited by Dave Humphries; 12th April 2010 at 07:41 PM.

  18. #18
    arith's Avatar
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    Re: That horrid CA

    Yes I like your flag and I do expect CA. But the lens I'm using has CA 1.25 pixels at this aperture and the smaller the aperture the worse it gets.

    So instead of struggling I thought why not choose a better lens, trouble is I've got a 10D which is great by the way but has a full size mirror that moves forward.

    The L types are not even good when looking at CA except the most expensive of them and they are all expensive, the third types say AF not for ATPS-H hope I got that right but you know what I mean; it has to be EF for my camera otherwise if it is really shortbacked I get broke camera possibly lens as well.

    So I thought maybe I could use that lens the fifty nifty I bought just for portraits of my granddaughter, it is about the same width as my 28mm on a full frame but NO CA.

    Cheaper way to do it, it seems is to get a mint 5D. I get extra pixels as well because I'm crap at composing a scene or completely wrong mostly anyway, and it is cheaper. I just have to remember to keep the 28mm away from high contrast and the 50mm away from rough use for instance putting big filters on it. In the fullness of time I will be able to afford a good lens for it, but if I upgrade to say a Tokina I ain't gonna be able to afford a new camera for a very long time.
    Last edited by arith; 12th April 2010 at 08:29 PM.

  19. #19

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    Re: That horrid CA


    I don't know what You must do,because any action asks money.About the lenses all of mine,for Your quitness, have around 1.5px,but Capture NX does its duty.I'll disapoint You but in my opinion a good lens asks a good camera and a good camera asks a good lens and both ask money,much money for decent results not for very good ones.So in such conditions there is no problem.We must take the things as they are and go on.
    Radu Dinu

  20. #20
    arith's Avatar
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    Re: That horrid CA

    I sort of understand what you mean; a good camera demands a good lens. Actually if I don't aim for high contrast the 28mm is good and very sharp, but the 50mm has no CA problems. I haven't got piles of money and the very good advice is to go for the right lens; wrong in my case because then I will be stuck with the camera I've got for a very long time.

    I could use some extra pixels because it would be easier to compose and crop, and I can use the wideness; I've never actually got on with a cropped sensor and always surprised with the narrow view.

    At school I was taught with a medium format and that is the way I think, so cropped 1.6 thing is really catching me out with dof and just about everything.

    I'm just saying the crop is just too small especially with lenses designed for 35mm, and so I'm saving or starving for full format.

    cheers Steve

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