Before we start, let me be very clear: this is a non-scientific test. Everything was done handheld. So, take it with a large pinch of salt. The lenses were used on the NEX-5N with an APS-C size sensor, so the edge we talk about here, is not the true edge of the lens in full frame. Please keep this in mind.
Chinon 55mm f1.4 on left. Mamiya Sekor 55mm f1.4 on right. Click for larger image. Note file marks on the Mamiya on the aperture ring.
Note similar coating on both lenses. Click for larger image.
The Chinon 55mm f1.4 has a slightly larger lens barrel with a 55mm filter size, whereas the Mamiya Sekor is a bit smaller with a 52mm filter size. The Mamiya lacks a A/M switch to allow manually setting the lens aperture. You would need to buy an adapter that has a ring at the rear that pushes the aperture pin, or like I did, glue the pin down so that aperture can be selected. Also, the Mamiya has a proprietory locking mechanism, which prevents the aperture ring from turning when mounted on the adapter. I had to file that ring off so that the aperture ring can be turned.
From f1.4 to F8
Center of Image. Click to see 100% Crop
Far Edge of image. Click to see 100% Crop
As you can see, there isn't a significant amount of differences between the two lenses, especially when stopped down a little, and the bokeh is nice. Both are very sharp, though contrast is a bit low at f1.4, but improved a lot by f2.0. These lenses are fantastic choices for low light shooting. The ambiance and atmosphere is hard to recreate with a smaller aperture lens. No, they won't replace the auto focus lenses for action oriented shots, but with practice, one can shoot with relatively good accuracy and reasonably fast in many kinds of situation, especially with the aid of Focus Peaking of the NEX cameras. Even better, with an EVF.
Bokeh -- See any difference? Click for larger picture.
So, why would you pay more for the equivalent of a Tomioka 55mm f1.4? I guess some just like to own a lens with the Tomioka name on it. If you are looking for a lens for your own use, with the same image quality as the more expensive Tomioka, the Chinon, Mamiya Sekor, or Cosina versions are significantly cheaper. The choice, of course, is yours.
Below are couple more sample images from the Mamiya Sekor 55mm f1.4.
Bokeh -- NEX-5N & Mamiya Sekor 55mm f1.4. Click for larger image.
Statues -- NEX-5N & Mamiya Sekor 55mm f1.4 @ f4. Click for larger image.