Rokinon 12mm F2.0 for Sony NEX: vignetting? yes!

[This is my fifth blog post about the new Rokinon ultra wide angle 12mm (18mm-equiv) lens for Sony NEX.]

The other day, before walking into my office, I took the following shots from the office parking lot basically aiming for a satellite dish on a far-off tower.  Being a wide angle lens, the tower was considerably closer than it appears in the photos.

Anyway, I wanted to test vignetting, the existence of which had been quite obvious in my early images.  There are four images here, shot sequentially at F2, F4, F8 and F16.

There is significant vignetting in my opinion, with more of it when shot wide open and less of it when stopped way down.  But even at F16, it is there.

I was disappointed to see it so prevalent.  This is my first lens wider than 24mm-equiv.  Perhaps this is just the nature of the beast.  But it also occurs to me that this lens may be no different in this characteristic than native wide angle lenses from the major brands.  The difference is that with native lenses (e.g. Olympus lens on an Olympus camera) the in-camera processing can rid the image of the vignetting.

Yes, all of these images below can be post-processed (my preference is Lightroom) to remove vignetting.  However, the F2 vignetting is very problematic.  To get rid of it completely requires so much brightening that there is a loss of color in some situations.

Note:  At this size of 750 pixels wide (compared with viewing on my 24" monitor) it's difficult to see the vignetting, except perhaps at F2.  In fact it is only at F16 that you can see how really dirty my sensor is.  On my computer monitor I can see dirt at F4 and F8.

I am working on processing these same images so I can post BEFORE and AFTER  images.  Each one needs some work.

F2 - very obvious vignetting, corners plus edges