Color Fringing?

Discussion in 'Photography Beginners' Forum' started by Stamp, Jan 2, 2010.

  1. Stamp

    Stamp TPF Noob!

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    Took a few shots today with the Minolta 50mm f/1.7. I blew this one up 200% and noticed some green tones around the black lettering that wasn't exactly in focus, but close to it... I'm guessing this is an example of color fringing? What causes it? Kurt Munger seems to say color fringing is low here, but this looks like quite a bit to me. Minolta AF 50mm F/1.7 lens review

    What say you?

    [​IMG]

    200%
    [​IMG]
     
  2. Josh66

    Josh66 Been spending a lot of time on here!

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    High contrast.

    The black text against the white background in your example.
     
  3. KmH

    KmH Helping photographers learn to fish Supporting Member

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    A lot of people starting to go overboard with the shallow DOF.

    I'd be more concerned with the technical execution of the image, than I would about color fringing.

    As it is most of the fringing is in the OOF portion of the image.

    Extremely shallow DOF will be taking over from selective coloring as the campy, but ill applied, technique of the coming decade and I'm begining my crusade against it early on. :lmao:
     
  4. Stamp

    Stamp TPF Noob!

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    As I didn't ask for any C&C, I didn't expect any, as this is me still learning things with my camera/lens combos. The reason I posted, was about the fringing, I could care less about the "technical execution", because I wasn't trying to get this one in National Geographic.

    Thanks for your input on the actual question asked though. I'll remember to not post any pictures for a visual example of a problem or concern anymore. ;)
     
  5. DevilDogge

    DevilDogge TPF Noob!

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    Wow.. Modern art isn't my style, but I don't go around bashing it. Now I remember why I stopped going to forums....
     
  6. Derrel

    Derrel Mr. Rain Cloud

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    What you are seeing in longitudinal chromatic aberration, which is the worst type. It occurs at the edges of high-contrast subject matter in front of and behind the point of sharp focus: notice that there is virtually NO chromatic aberration on the in-focus letters but there is a pronounced and severe amount of it in the out of focus areas??? That is how we know this is longitudinal chromatic aberration and not lateral CA.

    Longitudinal chromatic aberration has fairly recently become known by a couple of names, which I put in my subject line for those who might,someday,maybe, do a search on CA. CA stands for Chromatic Aberration, and the new "internet" names for longitudinal CA are "bokeh chromatic aberration", or "bokeh CA", as well as "LoCa".

    Longitudinal chromatic aberration is usually most pronounced at wider apertures on a lens that has this optical defect. It can not be automatically mapped out by the CA-reduction software inside the newer Nikon cameras, nor can it be mapped out in software that Nikon,Canon,and Adobe have; it is fairly easy to remove lateral CA, but longitudinal CA is not such an easy to defeat foe.
     
  7. Montana

    Montana TPF Noob!

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    What Derrel said, and also stop looking at your images at 200%.
     
  8. Josh66

    Josh66 Been spending a lot of time on here!

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    +1
     
  9. Stamp

    Stamp TPF Noob!

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    Thanks for the helpful input, Derrel. As I understand it, CA hits digital harder than film, so they didn't put the special coatings on the lenses back then? That would make sense since this is an old Minolta film lens.
     
  10. Stamp

    Stamp TPF Noob!

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    I guess I'm just picky. :greenpbl:
     
  11. Derrel

    Derrel Mr. Rain Cloud

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    Well, I went and looked at the on-line lens review you referenced above, and there's a huge problem with the reviewer's understanding, obviously.


    The on-line reviewer whose web page your looked at wrote, "color fringing is light and poses no problems, it looks better wide open than the Sony 50mm F/1.4 does, but from F/1.7 and down, it's about the same."

    Uh...the tip-off is the use of the word "color fringing" to describe a fairly complicated optical problem. First, the term "color fringing" is not the correct term,and it totally,totally ignores longitudinal CA: for example, an amateur lens tester, like the guy who wrote the fan-review above uses the wrong term to describe CA, AND the lens you have exhibits the problem of Longitiudinal CA very,very badly.

    Obviously, if some internet wannabe' lens "tester" shoots a flat chart, and everything is in-focus and on a single plane of focus, there will be very little longitudinal "color fringing",since everything on the exact plane of focus is good,longitudinally, but that does not address lateral CA. As your angled photo, with differing depths shows, there is very little lateral chromatic aberrration at the edges of the in-focus lettering, but there is a hint of latral CA around the in-focus letters. However, the lens exhibits positively HUGE amounts of longitudinal chromatic aberration. So, the on-line lens review the fellow did really is not what I'd call a reliable source of information.

    So, basically, the internet lens fan who wrote the "review" used the wrong term to describe lateral CA, and ignored (probably through ignorance) the immense longitudial chromatic aberration the lens model exhibits. So, if you want a lens that is capable of doing the kind of shots you showed, you obviously need a lens that is much less prone to "LoCa" or "bokeh CA" at wide apertures. This type of bad bokeh CA is not a lens-to-lens defect; pretty much any lens of that same exact design and make will exhibit the same problem, so another copy of the 50/1.7 will have the same characteristic. This problem would be less-visible if the lens had been stopped down three stops or so, but then the bokeh would be different...
     
  12. KmH

    KmH Helping photographers learn to fish Supporting Member

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    My post wasn't meant to be serious. Hence, the :lmao:.

    I'm sorry, that you didn't get it.
     

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