New aspheric lens elements used in 42.5mm
IR posted some details on Panasonic's improvement in the mold making process over the past couple of year. The 42.5mm is the first lens to take advantage of these new lens elements.
"Panasonic provided the illustration above, showing the progress they've made in reducing onion-ring artifacts. The image on the far right shows where they started from, a couple of years ago. After a year of development effort, they reduced the onion ring effect to the extent shown in the center image. Finally, after an additional 6 months of work, they achieved the level seen on the left, a remarkable improvement. The final image on the left is an example of a lens made from a mold with a 20nm peak to valley surface roughness described earlier.
As you can see, there's really no sign of onion-ring bokeh in the final image above. Notably, this image is from the recently-announced Panasonic Leica 42.5mm f/1.2 DG Nocticron lens, so it's an example of what can be expected from Panasonic's advanced mold-making technology when applied to a real-world optic."