I wanted a prime that I could use all the time on my Sony Alpha 6000 and the Sigma 19mm f2.8 fit the bill. Its not expensive and has the same sharpness and level of quality as you would expect from any prime. Its effective focal length after the APSC crop factor is very usable in most situations.
I do not want to compare this with a Zeiss prime. Dxo mark says it has an effective sharpness of 10 P-Mpix. Trust me - its pretty good. You will not complain.
The lens is ok wide open and very sharp...

perfect for mya6000.
19mm is good FL for landscapes and the sharpness is great.

wish the slider was a bit more grippy. but a good purchase overall.

The lens is not very sharp in the middle but quite good at the corners. Good lens at this price.

Bang for the buck. Had doubts on the seller but got the product delivered on time and as described.

Update.
The lens is sharp good for landscape photography.

Very ideal for landscape photography as it is a wide angle lens.