Lens Assistance: K-50
I'm in the process of choosing a lens for my Pentax K-50 for a backcountry hiking trip west and could use some solid input from those more seasoned. I've been using the kit lenses that came with the K-50 and on the whole I am pleased with their performance given they are kit lenses.
However, I noticed that images are softer and a bit less sharp than I desire, especially on the 18mm end.
My key needs in a lens(es) are:
Sharpness, Low light performance, at least 35mm (18mm would be great)
Things I could care less about: motor noise,
Im on a budget, my max would be just north of $350-400. I'm fine achieving these needs in a single lens or a handful or primes. What are your thoughts/experiences? I mainly shoot portraits and landscapes. Weight is important but not a lens killer if it comes down to quality.
Here are a few I found- thoughts and do you think they would satisfy my equipment needs?
Tamron 28-75mm f/2.8 XR - I like what I have read so far, but would I be better off spending that $$ or a few primes? If so, what would you pick?
Pentax 21987 DA 35mm f/2.4
Sigma 18-250mm f3.5-6.3 DC MACRO HSM - much more range than what I need, but looks like a decent all around shooter, not sold on it yet though.
Side note: my experience with lenses has been with weather resistant lenses. My main environment for shooting is outside on the trails (which is why I chose the K50). Will a non WR lens be a HUGE issue or, if I am careful, is it a plausible option? How essential, would you say, is WR?
Thanks much in advance for any help!