For quite a while the web-o-sphere has been shaping our desires when it comes to the gear we lust after. The Shelby Cobras of the lens world are the fast glass crowd. If you are looking for an 85mm portrait lens chances are you're lusting for an f1.4 or even an f1.2, even though you know that the f1.8 or the f2.8 will all function very well at the aperture of f4 you'll need to keep someone's face in sharp focus.... In the 50mm's we've been locked in a love hate relationship with the ultra fast fifties since, well....the 50's.
Even in micro four thirds and the Nex family the underlying rythme of the drums is a hope for more and more fast glass to come to market. So in the midst of all this Sigma goes all counterintuitive? What the heck are they thinking?
They've introduced two optics that are very interesting by dint of not being obviously interesting at all. They are a 19mm and a 30mm set of prime focal lengths with the plebeian maximum aperture of.....2.8. But before you dismiss them out of hand I have two cogent things to say that may push you to consider adding one or both to your selection/collection of optics for your mirrorless camera. 1. According to all accounts and every review site I've stumbled across in my Quixotic research, these lenses are both very sharp wide open and maintain that sharpness as they are stopped down. And, 2. They are tiny and dirt cheap. (That's actually three points altogether).
Each lens is available for around $199. They are plain matte black (think very discrete) and don't come with image stabilization. No big deal for Olympus shooters who have world class IS built in to their cameras but a possible non-starter for our shakier brethren shooting Sony Nex. What they do have is new configurations complete with aspheric elements and small, sharp elements.
Here's what Erwin Puts, the world's leading expert on Leica optics (with the exception of Leica engineers, of course) about slower lenses: (to paraphrase) Every time you increase the diameter of a lens element (essential in the design of fast glass) you increase the complexity of grinding and finishing that glass by a factor of 8X. It is far, far easier to design a high performance (meaning great image quality) lens with a slower (smaller) aperture than to make one with a large aperture.
And this is why most fast 50mm lenses, for example, are soft and of low contrast when used wide open, with atrocious corner performance, and only get better when stopped down a couple of stops. It is also why fast lenses that can be used at their maximum f-stops cost thousands of dollars.
I am putting down my keyboard in about 60 seconds to walk out the door, get in my car and drive over to Precision Camera to pick up a 30mm Sigma for the Nex that they have on hold for me. I haven't decided if I will also pick up the 19 mm but I sure am considering it. I'll have my first report on your desk in the morning. Bye.