Help with chromatic aberration

[jtiggatrost]

Can anyone help me please, i notice after editing my pictures in lightroom 4 that the leaves or whatever the picture is of, develops chromatic aberration. Help would be nice!

 

[480sparky]

CA isn't created in editing.... it's created when the image is taken.

 

[jtiggatrost]

so how do i prevent it from happening

 

[480sparky]

so how do i prevent it from happening

You can't, really..... it's a function of the lens. Some lenses are better than others in regards to CA, but it's just part of the laws of optics.

The best you can do in post is correct for it.

 

[Gavjenks]

Well there is at least one way you can prevent CA, but I don't think you're going to like it. Put a really dark monochrome filter on your lens. For instance, a dark green pass filter. Green is the best choice here, because your digital sensor probably has twice as many green "pixels" as other colors. Plus, your eye is most sensitive to green so you can compose better in low light.

This will result in green wavelength only images, which by definition cannot have different wavelengths splitting apart, because there's only one of them. The downside is that you then have to make the images black and white.

Otherwise buy a better lens as mentioned.

 

[KmH]

Most CA can be fixed with LR 4 - New Color Fringe Correction Controls

Adobe Photoshop Lightroom 4 Book: The Complete Guide for Photographers

With Lightroom open, press your keyboard F1 key and when the Adobe Community Help web site pops up navigate to a tutorial on how to use the Lens Correction panel.

 

[480sparky]

Well there is at least one way you can prevent CA, but I don't think you're going to like it. Put a really dark monochrome filter on your lens. For instance, a dark green pass filter. Green is the best choice here, because your digital sensor probably has twice as many green "pixels" as other colors. Plus, your eye is most sensitive to green so you can compose better in low light.

This will result in green wavelength only images, which by definition cannot have different wavelengths splitting apart, because there's only one of them. The downside is that you then have to make the images black and white.

Otherwise buy a better lens as mentioned.

Option 2: Shoot Black & White. :mrgreen:

 

[Gavjenks]

Well there is at least one way you can prevent CA, but I don't think you're going to like it. Put a really dark monochrome filter on your lens. For instance, a dark green pass filter. Green is the best choice here, because your digital sensor probably has twice as many green "pixels" as other colors. Plus, your eye is most sensitive to green so you can compose better in low light.

This will result in green wavelength only images, which by definition cannot have different wavelengths splitting apart, because there's only one of them. The downside is that you then have to make the images black and white.

Otherwise buy a better lens as mentioned.

Option 2: Shoot Black & White. :mrgreen:

Simply shooting in black and white (setting your camera to black and white, or using black and white film) does not prevent chromatic aberration!

The light hitting the sensor/film is still colored, and the different colors will still fall at slightly different locations if the lens has CA. It will show up as edge blur or if extreme, ghosting / seeing double

Color:


Simply shooting in black and white with no filter:


Filtering out all but one color optically, and setting your camera to B&W:





I suppose you could also just use one channel in photoshop instead, though. I'm not sure if there are any drawbacks to that compared to a filter...
Other than, of course, having to do stuff in post (an optical filter + B&W mode in camera = automatic single channel with no fiddling later on)

 

[Murray Bloom]

You can also fix CA in Photoshop. Filters>Lens Correction

 

[Gavjenks]

You can also fix CA in Photoshop. Filters>Lens Correction

It doesn't do a very good job with axial CA though.

Lateral CA = different colors basically have different zooms/magnification, so to correct, software just rescales two of the channels to be the same size as the third. Software is really good at this, even for unknown lenses.

Axial CA = the plane of focus is at different distances in front of you for different colors, so a near object might be in focus only in green, and a further object might be in focus only in red. So they both appear blurry slightly. Only really an issue with fairly narrow DOF, but when it is noticeable, it's really hard to correct in software, because your software doesn't know the depths of objects in a scene, so as far as it is concerned, blur is changing erratically and unpredictably over the image. Also, of course, blur in general is not possible to fix entirely in software, even if you did have exact depth information to work with.

 

[Murray Bloom]

That's true, but fortunately, I've never had a problem with axial CA. I'd think that it's lens-specific and stopping down could minimize or cure it. Yes?

 

[Gavjenks]

The extent to which it is present is lens specific yes. And stopping down should indeed reduce the issue.

 

[jtiggatrost]

ThAm you everyone I found out on Lightroom you can take away chromatic aberration and it works pretty good. Also I will try with the filters I have to see if that changes anything.