Image courtesy Robin Wong
Robin Wong posted his full Leica 12mm f/1.4 lens review:
What started out as a lens I was reluctant to review, became one that I actually enjoyed using tremendously.
Besides being a sharp wide angle lens, there is a pleasing quality to the way this lens renders the images. There is good amount of contrast and pop, creating a 3-D look which I normally do not see from wide angle lenses. Bokeh quality is excellent and autofocus works flawlessly. Nonetheless, the Panasonic 12mm F1.4 is not without flaws – the corner softness and chromatic aberration can pose serious problems. The corner sharpness is so bad that you need to stop down to F4 for decent results. Purple fringing is noticeable in high contrast areas, and software correction cannot account for this very well.
Despite these flaws there is currently no other alternative to a wide angle F1.4 lens. There really is no benchmark to compare to. Perhaps, it is a huge challenge to create a 12mm lens with such a large aperture opening.
12mm f/1.4 at [shopcountry 61026].