A challenge to all Wetpixel members.
Those of you have played with the latest release of Lightroom may have found an apparently unwelcome surprise lurking within the Lens Correction tab of the Develop module. Previous versions of Lightroom have offered sliders to allow users to correct Chromatic Aberration in terms of colors, and a “Defringe” option.
In place of these controls, Lightroom 4 simply offers a check-box labelled “Remove Chromatic Aberration”.
Just to recap, CA is a:
“type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens). The refractive index decreases with increasing wavelength.
Chromatic aberration manifests itself as “fringes” of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point. Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions.” (Source: Wikipedia).
Underwater, the refractive index of water (as opposed to air) as well as the light moving through the optical glass in dome and flat ports or magnifying diopters, in addition the lens’s glass elements, means that there is often considerable CA in images. One response to this was the algorithm in Lightroom’s Develop module, and its associated sliders.
For Lightroom 4, Adobe has instituted an automatic CA control, that they feel, is so good that manual control is no longer warranted or needed.
In fact, they seem to recommend that the “Remove Chromatic Aberration” option is applied to entire libraries.
This has not met with universal approval. On the Adobe Labs, there are threads, some quite vituperative, devoted to asking Adobe to bring the controls back.
For my part, I have an in built resistance to an automatic adjustment, as I reason that one solution cannot correct the problem in all images. Both Wetpixel Publisher Eric Cheng and pro photographer Jason Bradley have tried to make the new process slip-up. Both have failed. I have also tried, and for the moment, also admit failure.
So the challenge to Wetpixel members is to beat the automatic process. If you have upgraded to Lightroom 4, please run your “worst” examples of CA through the new Lens Correction algorithm, ensuring that the “Remove Chromatic Aberration” tick box is ticked. If you get examples of it not having worked, please post before and after images in the thread that has been started on the forum. If you can’t beat it, please admit defeat in the forum post as well!