Here is the best organized information for Samsung NX lenses:
You will find a list of all their lenses and it shows where to find a review of each lens.
The lens specifications of a lens includes the aperture rating.
This /f number tells you how bright/dark the lens is.
The smaller the number the brighter the lens.
When you get to the brightest lens it will be f/1.4 (85mm).
But you will also find that it cost $1,000.
Their 45mm lens is f/1.8 and cost $300
Their 60mm lens is f/2.8 and cost $600 (because it is an OIS lens)
Most people usually end up picking a lens based on price.
I suggest you look at the reviews of those 3 lenses for details about their quality.
I've recently bought a Samsung NX-1000 and have three lenses: the kit lens 20-50 mm, 18-55 mm IOS, and 55-200 mm OIS. I'd like to get a prime lens between 20-40 mm, but I'm confused as to which one would be the best buy for low light, fairly distortion-free use. Can anyone give me their experience and opinion with primes in this range?