Does the aperture open up all the way or did they make a 1.4 lens and then just call it a 1.8 where aperture does not open up fully?
The lens has no vignetting at full aperture (1.8 ) according to the advertising. Maybe the reason also for no cat eye effect?
I just looked at images taken with the 0.95 Z Noct. It has a lot of cat eye effect when looking at official images.
Usually, to make a lens free of mechanical vignetting (which causes the cats-eye effect), the front and rear lens elements need to be large, so they won't clip peripheral light rays. However, if the designer goes to the effort of making large diameter lenses, they may as well make the lens faster - the marketing people like this because you can sell a faster lens at a higher price
So you end up with a faster lens with cats-eye effect and vignetting at full aperture, but with more even rendition when stopped down. Most lenses are like this, I imagine the cats-eye effect of the Z Noct largely goes away by f/1.2 or f/1.4. The Plena largely eliminates cat-eye at full aperture partly because it has a relatively long focal length - the narrow field of view means that even peripheral rays are not entering at much of an angle so are not clipped going through the lens. Also, the Z lens mount is very big - this enables the rear element to be very large, fully covering the sensor, while the front element can be normal size (for a lens of this type).
