With the 5D Mk-II getting all the attention, it would be easy to miss a very important launch. The new 24mm f/1.4L Mk-II has something special that other "L" lenses don't. We'll soon know if it'll save Canon's repution when it comes with wide-angle lenses.
The new secret sauce is in the coatings...
Sub Wavelength structure Coating
The 24mm F1.4 L USM II sees the debut of Canon's new 'Sub Wavelength structure Coating' (SWC) technology. Considered by Canon to be considerably more effective then their existing 'Super Spectra Coating', the new coating is applied to the inside surface of the front lens element, and is designed to minimize flare and ghosting caused by secondary reflections between the sensor surface and the lens elements, which can lead to significant image degradation in digital SLRs.
The new biomimetic coating is inspired by features found within the eyes of moths, and uses a nano-scale structure to reduce dramatically the amount of internally-reflected light in lenses that contain large curve-radius elements. It is therefore particularly effective with fast wideangles such as the new 24mm F1.4L II USM.
This is basically a response to Nikon’s “Nano” coating, which from engineering descriptions works the same way as SWC.
In turn both of these are responses to Zeiss' T* coatings, which I suspect aren't so technologically advanced as they are generously applied. In an interview with Nikon engineers the main guy let slip that they were gunning for T* when they brought the technology behind Nano to photographic lenses.
Nikon has a bit of a lead here, having deployed Nano in these lenses so far: 14-24, 24-70, 105 Micro, 60 Micro, 16-85, 300/2.8, 400/2.8, 500/4, 600/4.
In the end this is pretty awesome news for the “L” lenses going forward. To me that suggests that some of the old classics will see new versions, now that there's a compelling check box to add.