Originally posted by AggieDad The rave reviews about the viewfinder are a key issue for me with my 72 year old eyes. I would wish for a hinged screen as well, but the viewfinder has more weight for me.
I'm quoting this line from your original post because this seems to be a deciding factor for you. The one thing to keep in mind with the lenses you have selected is that although they are both highly regarded lenses,
they are on the slower side, so the view you get in your viewfinder is not going to be as bright as it could be. Not terrible, but dimmer than other options. Unfortunately, you'd probably have to spend a lot more on
your lenses to get something faster that will give you a brighter view in the viewfinder ( ie. lenses with lower min aperture ).
I find myself leaning towards faster lenses more and more - not because I want to shoot wide open, but because I want a bright view in my viewfinder. After you've been shooting with an f2.8 lens ( or faster ), it can be very irksome to
squint through a slow tele-zoom ( like my F 70-210 ).
There isn't much you can do on the long end - from what I gather, the 55-300 is a bargain in that zoom range. Note that slapping a 2x teleconverter is going to make the view through the viewfinder even darker.
On the wide end, you could opt for something like a Tamron 17-50 f2.8. It will give you a slightly wider angle of view, and a brigher view through the viewfinder than the 18-135. You'd be giving up WR and Quickshift,
which may both be important to you, depending on your shooting style. Price wise, they're probably similar, but you might be able to get a break on the 18-135 if you get it bundled with the K50.
Just something to keep in mind if the brightness of the viewfinder is important to you. If you can, try the lenses out on the camera body before buying, and compare them to faster options to see what you're giving up.
As I said, there's nothing wrong with the lenses you've picked.