Chromatic Aberration - Canon 6D

Discussion in 'Canon Lenses' started by Auzeras, Apr 28, 2014.

  1. Auzeras

    Auzeras TPF Noob!

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    I've had my Canon 6D for a few months now (since December '13) and recently I've noticed some chromatic aberration (cyan and magenta) around edges in my images, usually between areas of high contrast. In some images its not very apparent whilst in others it is quite strong, even when not zoomed in very far on the image. Of course it depends on the subject, on most you can't tell but on others once you notice it it seems more apparent. This could be me just over analysing though!

    Just wondering if this is normal for the sensor/lens or if I should be sending it back to Canon. I've never encountered it like this on a DSLR (although I've seen similar artefacts on imaging equipment with misaligned filters/sensor channels) before. Lens is the stock 24/105mm, all images shot in RAW and scaled up for easier viewing from 100-300% crops.

    Other than this (potential) aberration problem I'm absolutely loving it. Wallet still tingles a bit from the price but well worth it!


     

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  2. Dao

    Dao No longer a newbie, moving up!

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    Is there any screw-on type filter or add-on lens in front of the lens? Were shots taken with aperture wide open?
     
  3. Dao

    Dao No longer a newbie, moving up!

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    This is what slrgear.com said about the lens

    "Worst-case chromatic aberration is a bit high at maximum wide angle, but the low average levels there point to the CA being confined mostly to the corners. CA drops to very low levels over most of the rest of the lens' zoom range, rising only slightly at 105mm."

    And from photozone.de

    "Lateral chromatic aberrations (color shadows at harsh contrast transitions) are no deal breaker - they remain on a comparatively moderate level at all focal lengths. Typical for most standard zoom lenses they're most pronounced at 24mm averaging around 1.5px at the image borders, it's slightly less at other focal lengths. This is naturally visible when observing an image at 100% magnification on a screen but it's a lesser issue on prints unless you go for the extremes here. Lateral CAs are also easily correctable during post-processing (Canon's DPP does it for you for instance)."


    So at 24mm, it is a little bit high according to the above lens review sites.
     
  4. DaninMD

    DaninMD TPF Noob!

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    the issue you are having is with the lens, not the sensor.
     
  5. TCampbell

    TCampbell Been spending a lot of time on here!

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    This is always the lens - not the camera.

    In the same way that ordinary light splits into a rainbow when it passes through a prism, each glass element in your lens behaves like a prism. A single glass element would have strong CA, so an arrangement of two elements can be combined (an achromatic "doublet") where the 2nd lens is concave instead of convex and designed to recombine the rainbow back into a single white light again -- except it's not perfect. More elements can be added to attempt to refine the image.

    Better lenses do a much better job correcting for the problem. However, it's also possible for computer software to correct for this and many image adjustment/editing programs can fix it.
     
  6. Auzeras

    Auzeras TPF Noob!

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    No filter or anything, just stock lens. Tyre shot at 28mm f/9, Power pole at 24mm f/9, Street light at 28mm f/10

    My first thought for any sort of aberration would of course fall to the lens, but having worked on an imaging product that produced similar faults due to a damaged filter I assumed it was that. Once again assuming got me in trouble.

    I was looking back through some earlier images to see if the fault was present and found that the aberration is only evident with RAW images, .jpg's shot under the same conditions don't exhibit it. A bit of tweaking in lightroom reduces it to a similar level to those in .Jpg's processed on the camera. A bit more should get it near perfect.

    Conclusion - No fault with anything other than my judgement. Mild heart attack after finding it since no one I knew had seen such results. I bought the camera overseas as well, returning items for warranty from New Zealand is just not something anyone wants to deal with either!

    Thanks all :)
     

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