Napioa - Wind Origins

Napioa - Wind Origins
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I've read several informations here on Photo SE, as well as the wikipedia article on CA.

I understand that it is inevitable that some amount of chromatic aberration shows up for a particular lens, especially on the extreme cases: high contrast of colors/luminosity, etc.

But I'd like to know if there is any
technique one can do to -minimize- this when some photo opportunity arises;

eg: if i'm visiting some place and want a picture of a building, for example. i can't go "meh, too contrasty, results won't be good."

  • Would stop down the aperture help? I haven't tested it, but according to the causes of CA, it could help (bigger DoF, more things in focus, less specific color in different focus).
  • Other than that, nothing comes to mind..

I already got a prime lens for the extra oomph of image quality, but i want more :)

please no "buy better gear" of "fix it in post" answers..
Obviously, i can fix stuff in post, AND I DO. But i'd like to make the most of my gear, and spend maybe a bit more time taking a picture, and less on lightroom.

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3  
I know you said no "fix it in post" answers, but it is worth noting that this is something which can be corrected for reasonably well in RAW processing with a lens-specific profile. Some cameras will even do this as part of their in-camera jpeg conversion. – mattdm Mar 8 '11 at 23:42
2  
Wait, hold on, how is this not an exact duplicate of the question you link to? Or at least an update, asking for techniques to reduce where it can't be avoided? – mattdm Mar 8 '11 at 23:43
    
    
@mattdm & @Jay Lance Photography - its sort of a reformulation and call for specific solutions, when taking the picture. i don't really think this is noise. – JoséNunoFerreira Mar 9 '11 at 1:36
    
My concern about this approach: i think it only corrects for lateral color fringing, something that is subject independent, and lens specific. it's great, and i agree, recent nikons (gen 2 cameras, according to ken rockwell) do this, as well as probably all raw developing software. However, for particular high contrast subjects, i am not sure it works! (sorry about quoting controversial people like mr rockwell) – JoséNunoFerreira Mar 9 '11 at 1:50
up vote 10 down vote accepted

I don't think these are quite the answers you want, since all of them involve changing the composition in some form, and these are probably already obvious to you, but:

  • Wait until a different time of day (like evening or early morning or nighttime) so there is less contrast between the building and the sky. Or wait until a cloudy day.

  • Move to a different position so there is less contrast between the subject and the background (for example, get above the building so the ground is the background, or move to the other side of the building so you have hills behind it instead of a bright sky).

  • CA is generally worst at the edges of the frame. Recompose your picture to put the object in the middle of the frame, and plan to crop the picture so anything at the corners with lots of CA won't be in the final picture.

  • I know you said you didn't want to hear this, but it might have the largest impact: some lenses handle CA better than others. Get a different (typically more expensive) lens.

  • Plan to downsize the image or print it small, so the CA is less visible (CA a couple pixels wide might not be visible on a 4x6" print but will be blindingly obvious on a 16x20" poster).

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these are sort of the answers that i was hoping for! i've thought about the contrast/composition, but i'm sort of hoping to hear about more techniques, and spark some discussion. :) – JoséNunoFerreira Mar 9 '11 at 1:40
1  
Glad I could help... but if you want more discussion you shouldn't accept answers so quickly ;) – drewbenn Mar 9 '11 at 8:16

Would stop down the aperture help?

If the type of chromatic aberration you're talking about is longitudinal (front-to-back) and showing up as purple fringe, then stopping down will absolutely help reduce or eliminate the issue. Also controlling exposure so there are no blown highlights. Purple fringing is especially prominent when using a fast lens wide open on a sparkly (metal, jewelry) or backlit subject. You can also correct for this, to some degree, in post, but since correction typically means desaturating the purple to a certain degree, it doesn't work well if you have a lot of the same purple in the image.

With lateral (side-by-side) chromatic aberration, it depends on the individual lens. Some lenses can benefit by being opened up (surprisingly Nikon's 35/1.8 has its best CA performance wide open). But most lenses can have a "sweet spot" for CA, just as they can for sharpness. And wide open is usually going to be the weakest spot for sharpness, CA, and vignetting. You may not be able to eliminate lateral CA in-camera, but most post-processing applications can correct for it (and vignetting and distortion).

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  1. Avoid high contrast, especially bright backlit subjects
  2. If you have high contrast, keep it away from the edges. CA is worse around the perimeter of an image. Always look at the perimeter of an image in post — you'll find it more than you think.
  3. Avoid shooting a zoom at either the closest or furthest focal length. These tend to multiply the effect as the light is moving prismatically more and splitting the colors more widely before they hit the sensor, which is what causes CA. This means something like popping the 75-250 on instead of the 18-135 when you want to shoot at 125mm.
  4. As noted, prime lenses have less glass and "groups" to split colors, so they tend to substantially reduce CA. Shoot large, crop.
  5. Yep, better glass, Raw, and work it in post. Try DxO OpticsPro for noise and CA removal. Fully 1/4 of my shots have a little bit of CA or noise. I shoot nature and that's the hardest for CA, especially if you are shooting daytime and cloudless rather than golden hours.
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Put a colored filter on the lens, to let only one frequency pass. Then during post processing, optionally, convert pictures to black and white. ;-)

Another method is to use software to correct chromatic aberration, such as PTLens. Or use a modern camera system: MFT cameras correct chromatic aberration for certain lenses automatically.

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I have found the using lower ISO helps reduce chromatic aberration. I also shoot in RAW and correct it in lightroom whenever I encounter it in my images.

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The answer depends on what type of CA you're dealing with.

  • Lateral CA fix it in post. This is easy and effective, plus there's no shooting technique I know of to reduce it (other than zooming if the CA is worse at the wide end).

  • Longitudinal (axial) CA stop down

  • Purple fringing avoid strong contrasts, might help to underexpose to avoid sensor bloom.

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Chromatic aberrations are closely related to the construction of the lens itself, although the situation can be made worse if you stack lots of filters on the front.

The likes of Canon and Nikon would also say that their lenses perform better than others (or each other, for that matter), and there is an element of truth in that, although, whether some of the astronomical differences between two similar lenses is worth it, is a matter of personal choice.

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Buy a better lens.

Otherwise, shoot in RAW and fix it in post-processing.

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There's no way to avoid it since its inherent in the lens. A better quality lens will have less chromatic aberrations.

One way to correct it is using lightroom. Here's a quick tutorial: http://www.dpnotes.com/how-to-reduce-chromatic-aberration-using-adobe-photoshop-lightroom/

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