The Samyang 35mm F1.4 AS UMC wide-angle, with its f1.4 aperture, is made up of 12 elements in 10 groups. Its manual auto focus uses a floating focus mechanism for a better image quality on the whole range of focus distance.
And this design seems to be very efficient in term of image quality.
Let’s compare it with its Nikon competitor, the Nikon AF-S NIKKOR 35mm f/1.4G, to know how good this lens is.
As we can see in this DxOMark lens comparison on a Nikon D3x:
So, the Samyang 35mm F1.4 AS UMC is an excellent lens, that comes out of this tests with similar scores as its premium Nikon competitor. But, at a price point 3 times lower than the Nikon AF-S NIKKOR 35mm f/1.4G, $1797 vs $599, the Samyang 35mm F1.4 AS UMCis definitely a very good choice if you can live without an auto-focus.