# How do you correct chromatic aberrations?



## te4o (Dec 22, 2011)

Could you please explain how to correct chromatic aberrations in PP! I have never managed to achieve a good correction in Aperture alone. Don't know how to use PS CS5 even if I have it... (perhaps there is a smart way there) :-[, NIK doesn't offer this I think but not sure as quite new to me, and last but not least: DxO Optics Pro 7 for 99USD - until 24th Dec. I've never used it, but how is it integrated into an Aperture based workflow? I think Neuro mentioned he uses it on the PCvsMAC thread. Thanks for Your Effort! 
BTW I searched the forum and other sites but couldn't get a straight forward explanation. 
Ah, and I can't afford a 1Dx with automatic in-camera correction :'(

On the DxO Pro 7 topic: does anyone use Catapult to integrate it with Aperture and what are your impressions?


----------



## neuroanatomist (Dec 22, 2011)

I do use DxO, but hadn't heard of Catapult before...I'll give that a look. Currently, both are part of the workflow, but not integrated. I convert RAW to JPG using DxO and import both RAW and JPG into Aperture (I keep them in separate libraries, although that's not necessary). 

As for CA correction, both DxO and DPP have the ability to correct it for specific lenses, and the degree of correction can be modified. But, those only correct lateral CA (the red/blue fringing that's present mostly at the edges of the frame). Neither correct longitutinal CA (the purple/green fringing present throughout the frame with fast primes shot wide, sometimes called bokeh fringing because it's most evident in OOF areas of the image).

FWIW, the in-camera CA correction on the 1D X only applies to JPGs, and at best would be the same as DPP will do for a RAW image.


----------



## DJL329 (Dec 22, 2011)

neuroanatomist said:


> I do use DxO, but hadn't heard of Catapult before...I'll give that a look. Currently, both are part of the workflow, but not integrated. I convert RAW to JPG using DxO and import both RAW and JPG into Aperture (I keep them in separate libraries, although that's not necessary).
> 
> As for CA correction, both DxO and DPP have the ability to correct it for specific lenses, and the degree of correction can be modified. But, those only correct lateral CA (the red/blue fringing that's present mostly at the edges of the frame). Neither correct longitutinal CA (the purple/green fringing present throughout the frame with fast primes shot wide, sometimes called bokeh fringing because it's most evident in OOF areas of the image).
> 
> FWIW, the in-camera CA correction on the 1D X only applies to JPGs, and at best would be the same as DPP will do for a RAW image.



Neuro, which version of DxO do you use? I have DxO Optics Pro 6.6 and it fixes the purple CA for me. I do have to increase the "Intensity" and "Size" values (not to mention actually clicking the "Purple fringing" check box) to make it have a noticeable effect.

http://www.dxo.com/intl/photo/dxo_optics_pro/features/optics_geometry_corrections/aberration


----------



## neuroanatomist (Dec 22, 2011)

Thanks for the tip! To be honest, I hadn't ever noticed the PF correction option, or if I did, I completely forgot about it...but sure enough - there it is! I'll try it out next time I have images with that issue... (I'm using DxO v7.1, BTW.)


----------



## AprilForever (Dec 22, 2011)

I rarely bother to, unless it is severe, in which case I use Lightroom's or PS's functions for it... I rarely have much CA, though... Due to lens choices and subject, prolly... and likely partly due to not really caring a lot about it...


----------



## PaperTiger (Dec 22, 2011)

If I shoot a backlit subject with my 50mm 1.4 at F1.4 I can get some pretty harsh purple fringing - a good reason to keep the lens above F2.0. But the photos are usable with a little tweaking:

Like scrappydog said, desaturate the hue. I use Purple in the Lightroom colour sliders. It matches the fringing almost perfectly, and it's a hue that doesn't come up too often in photos so you won't have a bizarre grey spot elsewhere in the photo. A grey fringe is much less noticeable than a bright purple one. 

This only works if you've got little purple in the rest of the photo. It's much easier to control in Photoshop.

Red/Green aberration is a little more tricky and best left Canon Digital Raw or Photoshop.


----------



## Kernuak (Dec 22, 2011)

I tried a few options, although none of the ones mentioned above, but the best I have found is Lightroom. For most images, I set the defringing to all edges, then adjust the CA sliders to match the lens/image, reviewing manually. Once i know a lens, I have a pretty good idea of where to set it. In scenes with a lot of high contrast areas, I set the defringing to highlight edges only, to prevent a grey line appearing along the transtion areas (particilarly the horizon). It isn't perfect, but it removes enough to stop it being obvious without pixel peeping (and then you have to look quite hard most of the time). I've never been able to see it in an A3 print from either the 7D or 5D MkII using this method. Mind you, the lenses I usually use with the 7D don't tend to have a large problem with fringing or CA, unlike those I tend to use on the 5D MKII.


----------



## Flake (Dec 22, 2011)

A couple of points slightly away from the original question.
CAs are one of the issues which more expensive lenses deal with better than the cheaper one (or are supposed to) so the first question would be what lens are you using.
Secondly you can minimise the effect by knowing when it is likely to occur (high contrast). Light through trees is often difficult, borders and corners are often worse than centres.
Filters, if you have a protective filter on - try taking it off and comparing results, often they aren't as good as you might think and can have quite a bad effect.

It's always better getting it right in camera rather than correcting it in post


----------



## friedmud (Dec 22, 2011)

I hate to be "that guy", but I did just want to mention that the CA correction in Lightroom 3 has been flawless for me. I just enable "Lens Corrections" and magically CA and vignetting goes away (LR3 know about most every lens).

Just throwing that out there in case someone is reading this and trying to decide between tools.


----------



## smirkypants (Dec 22, 2011)

friedmud said:


> I did just want to mention that the CA correction in Lightroom 3 has been flawless for me. I just enable "Lens Corrections" and magically CA and vignetting goes away (LR3 know about most every lens).


Ditto for Adobe Camera Raw (which is basically Lightroom). Just choose your lens and boom! It's gone. I'm not sure if it works with JPEG files, though. I only shoot RAW.


----------



## te4o (Dec 22, 2011)

Thanks for your replies!
I understand that CA elimination is done on the basis of lens presets within the software (Aperture doesn't seem to have it). If there is no preset for the lens then there is no automatic correction... 
I use exclusively CZ ZE primes and often wide open - and yes, there is not very often much CA but sometimes the [email protected] goes purple. I presume that CA will become a bigger issue on a higher MP sensor. That's why I am asking.
Thank you for your suggestions, I'll try the PS selecting tool or even the NIK control points to selectively desaturate the purple edges in the trees (thanx Flake, that's exactly where I hate CA).
B+W 010 UV on vs off didn't make much difference, and somehow I don't want to stop down all the time...


----------

